WD-repeats are motifs that are found in a variety of proteins and are characterized by a conserved core of 40-60 amino acids that commonly form a tertiary propeller structure. While proteins that contain WD-repeats participate in a wide range of cellular functions, they are generally involved in regulatory mechanisms concerning chromatin assembly, cell cycle control, signal transduction, RNA processing, apoptosis and vesicular trafficking. Tomosyn, also known as STXBP5 (syntaxin binding protein 5), LLGL3 or LGL3, is a 1,151 amino acid protein that localizes to the cytoplasm, as well as to the cell junction, secretory vesicles and to the peripheral membrane and contains one v-SNARE coiled-coil homology domain and 14 WD repeats. Interacting with Syntaxin 1 and Syntaxin 1B, Tomosyn functions as a regulator of neurotransmitter release and calcium-dependent exocytosis. Additionally, Tomosyn inhibits membrane fusion and may play a role in the assembly of SNARE complexes between transport vesicles and the plasma membrane. Multiple isoforms of Tomosyn exist due to alternative splicing events.
Function:
Tomosyn plays a regulatory role in calcium-dependent exocytosis and neurotransmitter release by inhibiting the assembly of trans-SNARE complexes between transport vesicles and the plasma membrane, via the displacement of munc18 from syntaxin-1. There are three splice variants of tomosyn designated m-tomosyn, b-tomosyn and s-tomosyn. Although b-tomosyn is ubiquitously expressed, s-tomosyn and m-tomosyn are expressed primarily in brain.
Subunit:
Interacts with STX1A and STX1B via its v-SNARE homology domain. Part of a complex that contains STX1, STXBP5, SNAP25 and SYT1. Part of a complex that contains STXBP5, STX4A and SNAP23.
Subcellular Location:
Cytoplasm. Cell membrane; Peripheral membrane protein. Cytoplasmic vesicle membrane; Peripheral membrane protein. Cytoplasmic vesicle, secretory vesicle, synaptic vesicle. Cell junction, synapse. Note=Cytoplasmic, and associated with vesicular membranes and the plasma membrane. Detected at synapses and on synaptic vesicles.
Similarity:
Belongs to the WD repeat L(2)GL family.
Contains 1 v-SNARE coiled-coil homology domain.
Contains 14 WD repeats.
SWISS:
Q5T5C0
Gene ID:
134957
Database links:
Entrez Gene: 134957 Human
Entrez Gene: 71768 Mouse
Entrez Gene: 81022 Rat
Omim: 604586 Human
SwissProt: Q5T5C0 Human
SwissProt: Q8K400 Mouse
SwissProt: Q9WU70 Rat
Unigene: 93534 Human
Unigene: 331751 Mouse
Unigene: 96029 Rat
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