V-type

proton ATPase In the field of enzymology, a proton ATPase is an enzyme that catalyzes the following chemical reaction: :ATP + + in \rightleftharpoons ADP + phosphate + out The 3 substrates of this enzyme are ATP, , and , whereas its 3 products are ADP, ph ...

21 kDa

proteolipid A proteolipid is a protein covalently linked to lipid molecules, which can be fatty acids, isoprenoids or sterols. The process of such a linkage is known as protein lipidation, and falls into the wider category of acylation and post-translationa ...

subunit is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

that in humans is encoded by the ''ATP6V0B''

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

. This gene encodes a component of

vacuolar ATPase Vacuolar-type ATPase (V-ATPase) is a highly conserved evolutionarily ancient enzyme with remarkably diverse functions in eukaryotic organisms. V-ATPases acidify a wide array of intracellular organelles and pumps protons across the plasm ...

(V-ATPase), a multisubunit enzyme that mediates acidification of

eukaryotic Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

intracellular

organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the ...

s. V-ATPase dependent organelle acidification is necessary for such intracellular processes as

protein sorting :''This article deals with protein targeting in eukaryotes unless specified otherwise.'' Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations within or outside the ce ...

zymogen In biochemistry, a zymogen (), also called a proenzyme (), is an inactive precursor of an enzyme. A zymogen requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active ...

activation,

receptor-mediated endocytosis Receptor-mediated endocytosis (RME), also called clathrin-mediated endocytosis, is a process by which cells absorb metabolites, hormones, proteins – and in some cases viruses – by the inward budding of the plasma membrane (invagination). Thi ...

, and

synaptic vesicle In a neuron, synaptic vesicles (or neurotransmitter vesicles) store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulse ...

proton gradient An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and th ...

generation. V-ATPase is composed of a

cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells (intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...

ic V1 domain and a transmembrane V0 domain. The V1 domain consists of three A and three B subunits, two G subunits, plus the C, D, E, F, and H subunits. The V1 domain contains the ATP

catalytic Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

site. The V0 domain consists of five different subunits: a, c, c', c'', and d. Additional

isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some isof ...

s of many of the V1 and V0 subunit proteins are encoded by multiple genes, or alternatively spliced transcript variants. This encoded protein is part of the transmembrane V0 domain, and is the human counterpart of

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

VMA16. Two alternatively spliced transcript variants that encode different proteins have been found for this gene.

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Further reading