Synaptobrevin
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Synaptobrevins (''synaptobrevin isotypes 1-2'') are small
integral membrane proteins An integral, or intrinsic, membrane protein (IMP) is a type of membrane protein that is permanently attached to the biological membrane. All transmembrane proteins can be classified as IMPs, but not all IMPs are transmembrane proteins. IMPs com ...
of secretory vesicles with
molecular weight A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...
of 18
kilodalton The dalton or unified atomic mass unit (symbols: Da or u, respectively) is a unit of mass defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. It is a non-SI unit accepted f ...
(kDa) that are part of the vesicle-associated membrane protein (VAMP) family. Synaptobrevin is one of the SNARE proteins involved in formation of the SNARE complexes.


Structure

Out of four α-helices of the core SNARE complex one is contributed by synaptobrevin, one by
syntaxin Syntaxins are a family of membrane integrated Q-SNARE proteins participating in exocytosis. Domains Syntaxins possess a single C-terminal transmembrane domain, a SNARE domain (known as H3), and an N-terminal regulatory domain (Habc). Syntaxi ...
, and two by SNAP-25 (in neurons).


Function

SNARE proteins are the key components of the molecular machinery that drives fusion of membranes in
exocytosis Exocytosis is a term for the active transport process that transports large molecules from cell to the extracellular area. Hormones, proteins and neurotransmitters are examples of large molecules that can be transported out of the cell. Exocytosis ...
. Their function however is subject to fine-tuning by various regulatory proteins collectively referred to as ''SNARE masters''.


Classification

In the Q/R
nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. (The theoretical field studying nomenclature is sometimes referred to as ''onymology'' or ''taxonymy'' ). The principl ...
for organizing SNARE proteins, VAMP/synaptobrevin family members are classified as R-SNAREs, so named for the presence of an
arginine Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidinium, guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) a ...
at a specific location within the primary sequence of the protein (as opposed to the SNAREs of the target membrane, which contain a
glutamine Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral ...
and are so named Q-SNAREs). Synaptobrevin is classified as a V-SNARE in the V/T nomenclature, an alternative classification scheme in which SNAREs are classified as V-SNAREs and T-SNAREs for their localization to vesicles and target membranes, respectively.Juan S. Bonifacino and Benjamin S. Glick. "The Mechanisms of Vesicle Budding and Fusion." Cell, Vol. 116, 153–166, January 23, 2004,


Clinical significance

Synaptobrevin is degraded by tetanospasmin, a protein derived from the bacterium '' Clostridium tetani'', which causes
tetanus Tetanus (), also known as lockjaw, is a bacterial infection caused by ''Clostridium tetani'' and characterized by muscle spasms. In the most common type, the spasms begin in the jaw and then progress to the rest of the body. Each spasm usually l ...
. A related bacterium, ''
Clostridium botulinum ''Clostridium botulinum'' is a Gram-positive bacteria, gram-positive, Bacillus (shape), rod-shaped, Anaerobic organism, anaerobic, endospore, spore-forming, Motility, motile bacterium with the ability to produce botulinum toxin, which is a neurot ...
'', produces the
botulinum toxin Botulinum toxin, or botulinum neurotoxin (commonly called botox), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon en ...
. Various botulinum toxin serotypes exist that each cleave specific peptide bonds of specific neuronal SNARE proteins, and synaptobrevin is this target protein for several of the serotypes.


Human proteins containing this domain

SEC22A; SEC22B; VAMP1; VAMP2;
VAMP3 Vesicle-associated membrane protein 3 is a protein that in humans is encoded by the ''VAMP3'' gene. Function Synaptobrevins/VAMPs, syntaxins, and the 25-kD synaptosomal-associated protein are the main components of a protein complex involved ...
;
VAMP4 Vesicle-associated membrane protein 4 is a protein that in humans is encoded by the ''VAMP4'' gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides i ...
; VAMP5; VAMP7; VAMP8; YKT6;


References and notes


External links

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Myobloc (rimabotulinumtoxinB) Prescribing Information
{{Vesicular transport proteins Protein domains Protein families Single-pass transmembrane proteins