P36536
uniprot
P36536
canonical
activity_regulation
ACTIVITY REGULATION: Small GTPases activation is mediated by guanine exchange factors (GEF), while inactivation through hydrolysis of the bound GTP is stimulated by GTPase activating proteins (GAP). Activated by the guanine nucleotide exchange factor PREB/SEC12 that facilitates the loading of SAR1B with GTP. {ECO:0000250|UniProtKB:Q9NR31}.
uniprot
proteins
amino_acid_sequence
MSFIFEWIYNGFSSVLQFLGLYKKSGKLVFLGLDNAGKTTLLQMLKDDRLGQHVPTLHPTSEELTIAGMTFTTFDLGGHEQARRVWKNYLPAINGIVFLVDCADHSRLMESKVELNALMTDETISNVPILILGNKIDRTDAISEEKLREIKGLYGQTTGKGNVTLKELNARPMEVFMCSVLKRQGYGEGFRWLSQYID
uniprot
proteins
ec_number
3.6.5.2
uniprot
proteins
function
FUNCTION: Small GTPase that cycles between an active GTP-bound and an inactive GDP-bound state and mainly functions in vesicle-mediated endoplasmic reticulum (ER) to Golgi transport. The active GTP-bound form inserts into the endoplasmic reticulum membrane where it recruits the remainder of the coat protein complex II/COPII. The coat protein complex II assembling and polymerizing on endoplasmic reticulum membrane is responsible for both the sorting of cargos and the deformation and budding of membranes into vesicles destined to the Golgi. The GTPase activity of SAR1 by controlling the timing of COPII budding regulates the size of the formed vesicles and is important for cargo selection depending on their size. Together with SEC16A, forms the organized scaffold defining endoplasmic reticulum exit sites (ERES), some specific domains of the endoplasmic reticulum where COPII vesicles form. In addition to its role in vesicle trafficking, can also function as a leucine sensor regulating TORC1 signaling and more indirectly cellular metabolism, growth and survival. In absence of leucine, interacts with the GATOR2 complex via MIOS and inhibits TORC1 signaling. The binding of leucine abrogates the interaction with GATOR2 and the inhibition of the TORC1 signaling. This function is completely independent of the GTPase activity of SAR1B. {ECO:0000250|UniProtKB:Q9NR31}.
uniprot
proteins
mass_dalton
22371
uniprot
proteins
protein_family
SAR1 family
uniprot
proteins
protein_family
Small GTPase superfamily
uniprot
proteins
pubmed
21183079
uniprot
proteins
pubmed
8262187
uniprot
proteins
sequence_length
198
uniprot
proteins
subcellular_location
SUBCELLULAR LOCATION: Endoplasmic reticulum membrane {ECO:0000250|UniProtKB:Q9NR31}; Peripheral membrane protein {ECO:0000250|UniProtKB:Q9NR31}. Golgi apparatus, Golgi stack membrane {ECO:0000250|UniProtKB:Q9NR31}; Peripheral membrane protein {ECO:0000250|UniProtKB:Q9NR31}. Cytoplasm, cytosol {ECO:0000250|UniProtKB:Q9NR31}. Lysosome membrane {ECO:0000250|UniProtKB:Q9NR31}. Note=Active at endoplasmic reticulum exit sites (ERES) where it inserts into the membrane and recruits the remainder of the coat protein complex II/COPII. Upon leucine deprivation, associates with lysosomal membranes to repress TORC1 signaling. {ECO:0000250|UniProtKB:Q9NR31}.
uniprot
proteins