2ROZ - JenaLib

NMR Structure(hide GO term definitions)

Chain A (A4_MOUSE | P12023)

molecular function
	GO:0003677	DNA binding	Any molecular function by which a gene product interacts selectively and non-covalently with DNA (deoxyribonucleic acid).
	GO:0051425	PTB domain binding	Interacting selectively and non-covalently with a phosphotyrosine-binding (PTB) domain of a protein.
	GO:0033130	acetylcholine receptor binding	Interacting selectively and non-covalently with an acetylcholine receptor.
	GO:0019899	enzyme binding	Interacting selectively and non-covalently with any enzyme.
	GO:0070851	growth factor receptor binding	Interacting selectively and non-covalently with a growth factor receptor.
	GO:0008201	heparin binding	Interacting selectively and non-covalently with heparin, any member of a group of glycosaminoglycans found mainly as an intracellular component of mast cells and which consist predominantly of alternating alpha-(1->4)-linked D-galactose and N-acetyl-D-glucosamine-6-sulfate residues.
	GO:0042802	identical protein binding	Interacting selectively and non-covalently with an identical protein or proteins.
	GO:0046872	metal ion binding	Interacting selectively and non-covalently with any metal ion.
	GO:0016504	peptidase activator activity	Binds to and increases the activity of a peptidase, any enzyme that catalyzes the hydrolysis peptide bonds.
	GO:0030414	peptidase inhibitor activity	Stops, prevents or reduces the activity of a peptidase, any enzyme that catalyzes the hydrolysis peptide bonds.
	GO:0005515	protein binding	Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
	GO:0005102	receptor binding	Interacting selectively and non-covalently with one or more specific sites on a receptor molecule, a macromolecule that undergoes combination with a hormone, neurotransmitter, drug or intracellular messenger to initiate a change in cell function.
	GO:0004867	serine-type endopeptidase inhibitor activity	Stops, prevents or reduces the activity of serine-type endopeptidases, enzymes that catalyze the hydrolysis of nonterminal peptide bonds in a polypeptide chain; a serine residue (and a histidine residue) are at the active center of the enzyme.
	GO:0046914	transition metal ion binding	Interacting selectively and non-covalently with a transition metal ions; a transition metal is an element whose atom has an incomplete d-subshell of extranuclear electrons, or which gives rise to a cation or cations with an incomplete d-subshell. Transition metals often have more than one valency state. Biologically relevant transition metals include vanadium, manganese, iron, copper, cobalt, nickel, molybdenum and silver.
biological process
	GO:0007219	Notch signaling pathway	A series of molecular signals initiated by the binding of an extracellular ligand to the receptor Notch on the surface of a target cell, and ending with regulation of a downstream cellular process, e.g. transcription.
	GO:0008344	adult locomotory behavior	Locomotory behavior in a fully developed and mature organism.
	GO:1990000	amyloid fibril formation	The generation of amyloid fibrils, insoluble fibrous protein aggregates exhibiting beta sheet structure, from proteins. An example of this is seen when human RIP1 and RIP3 kinases form a heterodimeric functional amyloid signaling complex (PMID:22817896).
	GO:0019731	antibacterial humoral response	An immune response against bacteria mediated through a body fluid. Examples of this process are the antibacterial humoral responses in Mus musculus and Drosophila melanogaster.
	GO:0019732	antifungal humoral response	An immune response against a fungus mediated through a body fluid. An example of this process is the antifungal humoral response in Drosophila melanogaster.
	GO:0006915	apoptotic process	A programmed cell death process which begins when a cell receives an internal (e.g. DNA damage) or external signal (e.g. an extracellular death ligand), and proceeds through a series of biochemical events (signaling pathway phase) which trigger an execution phase. The execution phase is the last step of an apoptotic process, and is typically characterized by rounding-up of the cell, retraction of pseudopodes, reduction of cellular volume (pyknosis), chromatin condensation, nuclear fragmentation (karyorrhexis), plasma membrane blebbing and fragmentation of the cell into apoptotic bodies. When the execution phase is completed, the cell has died.
	GO:0008088	axo-dendritic transport	The directed movement of organelles or molecules along microtubules in neuron projections.
	GO:0016199	axon midline choice point recognition	The recognition of molecules at the central nervous system midline choice point by an axon growth cone; this choice point determines whether the growth cone will cross the midline.
	GO:0007409	axonogenesis	De novo generation of a long process of a neuron, that carries efferent (outgoing) action potentials from the cell body towards target cells. Refers to the morphogenesis or creation of shape or form of the developing axon.
	GO:0007155	cell adhesion	The attachment of a cell, either to another cell or to an underlying substrate such as the extracellular matrix, via cell adhesion molecules.
	GO:0006878	cellular copper ion homeostasis	Any process involved in the maintenance of an internal steady state of copper ions at the level of a cell.
	GO:0009987	cellular process	Any process that is carried out at the cellular level, but not necessarily restricted to a single cell. For example, cell communication occurs among more than one cell, but occurs at the cellular level.
	GO:0071320	cellular response to cAMP	Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a cAMP (cyclic AMP, adenosine 3',5'-cyclophosphate) stimulus.
	GO:1990090	cellular response to nerve growth factor stimulus	A process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a nerve growth factor stimulus.
	GO:0071874	cellular response to norepinephrine stimulus	Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a norepinephrine stimulus. Norepinephrine is a catecholamine that has the formula C8H11NO3; it acts as a hormone, and as a neurotransmitter in most of the sympathetic nervous system.
	GO:0008203	cholesterol metabolic process	The chemical reactions and pathways involving cholesterol, cholest-5-en-3 beta-ol, the principal sterol of vertebrates and the precursor of many steroids, including bile acids and steroid hormones. It is a component of the plasma membrane lipid bilayer and of plasma lipoproteins and can be found in all animal tissues.
	GO:0048669	collateral sprouting in absence of injury	The process in which outgrowths develop from the axons of intact undamaged neurons.
	GO:0050829	defense response to Gram-negative bacterium	Reactions triggered in response to the presence of a Gram-negative bacterium that act to protect the cell or organism.
	GO:0050830	defense response to Gram-positive bacterium	Reactions triggered in response to the presence of a Gram-positive bacterium that act to protect the cell or organism.
	GO:0016358	dendrite development	The process whose specific outcome is the progression of the dendrite over time, from its formation to the mature structure. A dendrite is a freely branching protoplasmic process of a nerve cell.
	GO:0006897	endocytosis	A vesicle-mediated transport process in which cells take up external materials or membrane constituents by the invagination of a small region of the plasma membrane to form a new membrane-bounded vesicle.
	GO:0030198	extracellular matrix organization	A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of an extracellular matrix.
	GO:0030900	forebrain development	The process whose specific outcome is the progression of the forebrain over time, from its formation to the mature structure. The forebrain is the anterior of the three primary divisions of the developing chordate brain or the corresponding part of the adult brain (in vertebrates, includes especially the cerebral hemispheres, the thalamus, and the hypothalamus and especially in higher vertebrates is the main control center for sensory and associative information processing, visceral functions, and voluntary motor functions).
	GO:0045087	innate immune response	Innate immune responses are defense responses mediated by germline encoded components that directly recognize components of potential pathogens.
	GO:0035235	ionotropic glutamate receptor signaling pathway	A series of molecular signals initiated by glutamate binding to a glutamate receptor on the surface of the target cell, followed by the movement of ions through a channel in the receptor complex. Ends with regulation of a downstream cellular process, e.g. transcription.
	GO:0007626	locomotory behavior	The specific movement from place to place of an organism in response to external or internal stimuli. Locomotion of a whole organism in a manner dependent upon some combination of that organism's internal state and external conditions.
	GO:0006378	mRNA polyadenylation	The enzymatic addition of a sequence of 40-200 adenylyl residues at the 3' end of a eukaryotic mRNA primary transcript.
	GO:0007617	mating behavior	The behavioral interactions between organisms for the purpose of mating, or sexual reproduction resulting in the formation of zygotes.
	GO:0010951	negative regulation of endopeptidase activity	Any process that decreases the frequency, rate or extent of endopeptidase activity, the endohydrolysis of peptide bonds within proteins.
	GO:0045665	negative regulation of neuron differentiation	Any process that stops, prevents, or reduces the frequency, rate or extent of neuron differentiation.
	GO:0010466	negative regulation of peptidase activity	Any process that stops or reduces the rate of peptidase activity, the hydrolysis of peptide bonds within proteins.
	GO:0007399	nervous system development	The process whose specific outcome is the progression of nervous tissue over time, from its formation to its mature state.
	GO:0050885	neuromuscular process controlling balance	Any process that an organism uses to control its balance, the orientation of the organism (or the head of the organism) in relation to the source of gravity. In humans and animals, balance is perceived through visual cues, the labyrinth system of the inner ears and information from skin pressure receptors and muscle and joint receptors.
	GO:0051402	neuron apoptotic process	Any apoptotic process in a neuron, the basic cellular unit of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system.
	GO:0031175	neuron projection development	The process whose specific outcome is the progression of a neuron projection over time, from its formation to the mature structure. A neuron projection is any process extending from a neural cell, such as axons or dendrites (collectively called neurites).
	GO:0016322	neuron remodeling	The developmentally regulated remodeling of neuronal projections such as pruning to eliminate the extra dendrites and axons projections set up in early stages of nervous system development.
	GO:0010971	positive regulation of G2/M transition of mitotic cell cycle	Any process that increases the rate or extent of progression from G2 phase to M phase of the mitotic cell cycle.
	GO:0045931	positive regulation of mitotic cell cycle	Any process that activates or increases the rate or extent of progression through the mitotic cell cycle.
	GO:0010952	positive regulation of peptidase activity	Any process that increases the frequency, rate or extent of peptidase activity, the hydrolysis of peptide bonds within proteins.
	GO:0045944	positive regulation of transcription from RNA polymerase II promoter	Any process that activates or increases the frequency, rate or extent of transcription from an RNA polymerase II promoter.
	GO:0051260	protein homooligomerization	The process of creating protein oligomers, compounds composed of a small number, usually between three and ten, of identical component monomers. Oligomers may be formed by the polymerization of a number of monomers or the depolymerization of a large protein polymer.
	GO:0006468	protein phosphorylation	The process of introducing a phosphate group on to a protein.
	GO:0007176	regulation of epidermal growth factor-activated receptor activity	Any process that modulates the frequency, rate or extent of EGF-activated receptor activity.
	GO:0010468	regulation of gene expression	Any process that modulates the frequency, rate or extent of gene expression. Gene expression is the process in which a gene's coding sequence is converted into a mature gene product or products (proteins or RNA). This includes the production of an RNA transcript as well as any processing to produce a mature RNA product or an mRNA or circRNA (for protein-coding genes) and the translation of that mRNA or circRNA into protein. Protein maturation is included when required to form an active form of a product from an inactive precursor form.
	GO:0040014	regulation of multicellular organism growth	Any process that modulates the frequency, rate or extent of growth of the body of an organism so that it reaches its usual body size.
	GO:0043393	regulation of protein binding	Any process that modulates the frequency, rate or extent of protein binding.
	GO:0050803	regulation of synapse structure or activity	Any process that modulates the physical form or the activity of a synapse, the junction between a neuron and a target (neuron, muscle, or secretory cell).
	GO:0006417	regulation of translation	Any process that modulates the frequency, rate or extent of the chemical reactions and pathways resulting in the formation of proteins by the translation of mRNA or circRNA.
	GO:0010288	response to lead ion	Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a lead ion stimulus.
	GO:0006979	response to oxidative stress	Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of oxidative stress, a state often resulting from exposure to high levels of reactive oxygen species, e.g. superoxide anions, hydrogen peroxide (H2O2), and hydroxyl radicals.
	GO:0001878	response to yeast	Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus from a yeast species.
	GO:0051563	smooth endoplasmic reticulum calcium ion homeostasis	Any process involved in the maintenance of an internal steady state of calcium ions within the smooth endoplasmic reticulum of a cell or between the smooth endoplasmic reticulum and its surroundings.
	GO:0001967	suckling behavior	Specific behavior of a newborn or infant mammal that results in the derivation of nourishment from the breast.
	GO:0051124	synaptic growth at neuromuscular junction	The growth of a synapse at a neuromuscular junction, the site of apposition of a motor end plate and the subneural cleft of the skeletal muscle fiber that it innervates.
	GO:0008542	visual learning	Any process in an organism in which a change in behavior of an individual occurs in response to repeated exposure to a visual cue.
cellular component
	GO:0030134	COPII-coated ER to Golgi transport vesicle	A vesicle with a coat formed of the COPII coat complex proteins. The COPII coat complex is formed by the Sec23p/Sec24p and the Sec13p/Sec31p heterodimers. COPII-associated vesicles transport proteins from the rough endoplasmic reticulum to the Golgi apparatus (anterograde transport).
	GO:0005794	Golgi apparatus	A compound membranous cytoplasmic organelle of eukaryotic cells, consisting of flattened, ribosome-free vesicles arranged in a more or less regular stack. The Golgi apparatus differs from the endoplasmic reticulum in often having slightly thicker membranes, appearing in sections as a characteristic shallow semicircle so that the convex side (cis or entry face) abuts the endoplasmic reticulum, secretory vesicles emerging from the concave side (trans or exit face). In vertebrate cells there is usually one such organelle, while in invertebrates and plants, where they are known usually as dictyosomes, there may be several scattered in the cytoplasm. The Golgi apparatus processes proteins produced on the ribosomes of the rough endoplasmic reticulum; such processing includes modification of the core oligosaccharides of glycoproteins, and the sorting and packaging of proteins for transport to a variety of cellular locations. Three different regions of the Golgi are now recognized both in terms of structure and function: cis, in the vicinity of the cis face, trans, in the vicinity of the trans face, and medial, lying between the cis and trans regions.
	GO:0045177	apical part of cell	The region of a polarized cell that forms a tip or is distal to a base. For example, in a polarized epithelial cell, the apical region has an exposed surface and lies opposite to the basal lamina that separates the epithelium from other tissue.
	GO:0097449	astrocyte projection	A prolongation or process extending from the soma of an astrocyte and wrapping around neurons.
	GO:0030424	axon	The long process of a neuron that conducts nerve impulses, usually away from the cell body to the terminals and varicosities, which are sites of storage and release of neurotransmitter.
	GO:0009986	cell surface	The external part of the cell wall and/or plasma membrane.
	GO:0005911	cell-cell junction	A cell junction that forms a connection between two or more cells in a multicellular organism; excludes direct cytoplasmic junctions such as ring canals.
	GO:0035253	ciliary rootlet	A cytoskeleton-like structure, originating from the basal body at the proximal end of a cilium, and extending proximally toward the cell nucleus. Rootlets are typically 80-100 nm in diameter and contain cross striae distributed at regular intervals of approximately 55-70 nm.
	GO:0005905	clathrin-coated pit	A part of the endomembrane system in the form of an invagination of a membrane upon which a clathrin coat forms, and that can be converted by vesicle budding into a clathrin-coated vesicle. Coated pits form on the plasma membrane, where they are involved in receptor-mediated selective transport of many proteins and other macromolecules across the cell membrane, in the trans-Golgi network, and on some endosomes.
	GO:0005737	cytoplasm	All of the contents of a cell excluding the plasma membrane and nucleus, but including other subcellular structures.
	GO:0031410	cytoplasmic vesicle	A vesicle found in the cytoplasm of a cell.
	GO:0043198	dendritic shaft	Cylindric portion of the dendrite, directly stemming from the perikaryon, and carrying the dendritic spines.
	GO:0043197	dendritic spine	A small, membranous protrusion from a dendrite that forms a postsynaptic compartment - typically receiving input from a single presynapse. They function as partially isolated biochemical and an electrical compartments. Spine morphology is variable including "thin", "stubby", "mushroom", and "branched", with a continuum of intermediate morphologies. They typically terminate in a bulb shape, linked to the dendritic shaft by a restriction. Spine remodeling is though to be involved in synaptic plasticity.
	GO:0005768	endosome	A vacuole to which materials ingested by endocytosis are delivered.
	GO:0070062	extracellular exosome	A vesicle that is released into the extracellular region by fusion of the limiting endosomal membrane of a multivesicular body with the plasma membrane. Extracellular exosomes, also simply called exosomes, have a diameter of about 40-100 nm.
	GO:0005615	extracellular space	That part of a multicellular organism outside the cells proper, usually taken to be outside the plasma membranes, and occupied by fluid.
	GO:0030426	growth cone	The migrating motile tip of a growing nerve cell axon or dendrite.
	GO:1990812	growth cone filopodium	A thin, stiff protrusion extended by the leading edge of an axonal or dendritic growth cone.
	GO:1990761	growth cone lamellipodium	A thin sheetlike process extended by the leading edge of an axonal or dendritic growth cone; contains a dense meshwork of actin filaments.
	GO:0016021	integral component of membrane	The component of a membrane consisting of the gene products and protein complexes having at least some part of their peptide sequence embedded in the hydrophobic region of the membrane.
	GO:0043231	intracellular membrane-bounded organelle	Organized structure of distinctive morphology and function, bounded by a single or double lipid bilayer membrane and occurring within the cell. Includes the nucleus, mitochondria, plastids, vacuoles, and vesicles. Excludes the plasma membrane.
	GO:0044304	main axon	The main axonal trunk, as opposed to the collaterals; i.e., excluding collaterals, terminal, spines, or dendrites.
	GO:0016020	membrane	A lipid bilayer along with all the proteins and protein complexes embedded in it an attached to it.
	GO:0045121	membrane raft	Any of the small (10-200 nm), heterogeneous, highly dynamic, sterol- and sphingolipid-enriched membrane domains that compartmentalize cellular processes. Small rafts can sometimes be stabilized to form larger platforms through protein-protein and protein-lipid interactions.
	GO:0031594	neuromuscular junction	The junction between the axon of a motor neuron and a muscle fiber. In response to the arrival of action potentials, the presynaptic button releases molecules of neurotransmitters into the synaptic cleft. These diffuse across the cleft and transmit the signal to the postsynaptic membrane of the muscle fiber, leading to a change in post-synaptic potential.
	GO:0043005	neuron projection	A prolongation or process extending from a nerve cell, e.g. an axon or dendrite.
	GO:0005641	nuclear envelope lumen	The region between the two lipid bilayers of the nuclear envelope; 20-40 nm wide.
	GO:0048471	perinuclear region of cytoplasm	Cytoplasm situated near, or occurring around, the nucleus.
	GO:0005886	plasma membrane	The membrane surrounding a cell that separates the cell from its external environment. It consists of a phospholipid bilayer and associated proteins.
	GO:0043235	receptor complex	Any protein complex that undergoes combination with a hormone, neurotransmitter, drug or intracellular messenger to initiate a change in cell function.
	GO:0005791	rough endoplasmic reticulum	The rough (or granular) endoplasmic reticulum (ER) has ribosomes adhering to the outer surface; the ribosomes are the site of translation of the mRNA for those proteins which are either to be retained within the cisternae (ER-resident proteins), the proteins of the lysosomes, or the proteins destined for export from the cell. Glycoproteins undergo their initial glycosylation within the cisternae.
	GO:0005790	smooth endoplasmic reticulum	The smooth endoplasmic reticulum (smooth ER or SER) has no ribosomes attached to it. The smooth ER is the recipient of the proteins synthesized in the rough ER. Those proteins to be exported are passed to the Golgi complex, the resident proteins are returned to the rough ER and the lysosomal proteins after phosphorylation of their mannose residues are passed to the lysosomes. Glycosylation of the glycoproteins also continues. The smooth ER is the site of synthesis of lipids, including the phospholipids. The membranes of the smooth ER also contain enzymes that catalyze a series of reactions to detoxify both lipid-soluble drugs and harmful products of metabolism. Large quantities of certain compounds such as phenobarbital cause an increase in the amount of the smooth ER.
	GO:0051233	spindle midzone	The area in the center of the spindle where the spindle microtubules from opposite poles overlap.
	GO:0045202	synapse	The junction between a nerve fiber of one neuron and another neuron, muscle fiber or glial cell. As the nerve fiber approaches the synapse it enlarges into a specialized structure, the presynaptic nerve ending, which contains mitochondria and synaptic vesicles. At the tip of the nerve ending is the presynaptic membrane; facing it, and separated from it by a minute cleft (the synaptic cleft) is a specialized area of membrane on the receiving cell, known as the postsynaptic membrane. In response to the arrival of nerve impulses, the presynaptic nerve ending secretes molecules of neurotransmitters into the synaptic cleft. These diffuse across the cleft and transmit the signal to the postsynaptic membrane.
	GO:0043195	terminal bouton	Terminal inflated portion of the axon, containing the specialized apparatus necessary to release neurotransmitters. The axon terminus is considered to be the whole region of thickening and the terminal bouton is a specialized region of it.

Chain B (APBB2_MOUSE | Q9DBR4)

molecular function
	GO:0001540	amyloid-beta binding	Interacting selectively and non-covalently with amyloid-beta peptide/protein and/or its precursor.
	GO:0035035	histone acetyltransferase binding	Interacting selectively and non-covalently with the enzyme histone acetyltransferase.
	GO:0005515	protein binding	Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
	GO:0008134	transcription factor binding	Interacting selectively and non-covalently with a transcription factor, any protein required to initiate or regulate transcription.
biological process
	GO:0030048	actin filament-based movement	Movement of organelles or other particles along actin filaments, or sliding of actin filaments past each other, mediated by motor proteins.
	GO:0007411	axon guidance	The chemotaxis process that directs the migration of an axon growth cone to a specific target site in response to a combination of attractive and repulsive cues.
	GO:0007050	cell cycle arrest	A regulatory process that halts progression through the cell cycle during one of the normal phases (G1, S, G2, M).
	GO:0030198	extracellular matrix organization	A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of an extracellular matrix.
	GO:0043066	negative regulation of apoptotic process	Any process that stops, prevents, or reduces the frequency, rate or extent of cell death by apoptotic process.
	GO:0030308	negative regulation of cell growth	Any process that stops, prevents, or reduces the frequency, rate, extent or direction of cell growth.
	GO:0001764	neuron migration	The characteristic movement of an immature neuron from germinal zones to specific positions where they will reside as they mature.
	GO:0043065	positive regulation of apoptotic process	Any process that activates or increases the frequency, rate or extent of cell death by apoptotic process.
	GO:0050821	protein stabilization	Any process involved in maintaining the structure and integrity of a protein and preventing it from degradation or aggregation.
	GO:0006355	regulation of transcription, DNA-templated	Any process that modulates the frequency, rate or extent of cellular DNA-templated transcription.
cellular component
	GO:0005737	cytoplasm	All of the contents of a cell excluding the plasma membrane and nucleus, but including other subcellular structures.
	GO:0005634	nucleus	A membrane-bounded organelle of eukaryotic cells in which chromosomes are housed and replicated. In most cells, the nucleus contains all of the cell's chromosomes except the organellar chromosomes, and is the site of RNA synthesis and processing. In some species, or in specialized cell types, RNA metabolism or DNA replication may be absent.

Description

Compounds

Structural Features

Chains, Units

Ligands, Modified Residues, Ions (0, 0)

Sites (0, 0)

SS Bonds (0, 0)

Cis Peptide Bonds (1, 20)

Sequence-Structure Mapping

SAPs(SNPs)/Variants (0, 0)

PROSITE Motifs (2, 2)

Exons (0, 0)

Sequences/Alignments

Classification and Annotation

SCOP Domains (1, 1)

CATH Domains (0, 0)

Pfam Domains (2, 2)

Gene Ontology (117, 120)

Visualization

Interactive Views

Still Images

Databases and Analysis Tools

Databases

Analysis Tools

Related Entries

Entries Sharing at Least One Protein Chain (UniProt ID)

Related Entries Specified in the PDB File