Overview
| Uniprot ID | Q5PYH3 |
|---|
| Protein Name | Small COPII coat GTPase SAR1B |
|---|
| Gene Name | SAR1B |
|---|
| Organism | Sus scrofa |
|---|
Kla Sites from experimental identification
| Position |
Flanking peptide |
| 166 |
GKGSVSLKELNARPL |
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. In contrast to SAR1A, SAR1B specifically interacts with the cargo receptor SURF4 to mediate the transport of lipid-carrying lipoproteins including APOB and APOA1 from the endoplasmic reticulum to the Golgi and thereby, indirectly regulates lipid homeostasis. 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
Protein Sequence
10
MSFIFDWIYS
20
GFSSVLQFLG
30
LYKKTGKLVF
40
LGLDNAGKTT
50
LLHMLKDDRL
60
GQHVPTLHPT
70
SEELTIAGMT
80
FTTFDLGGHV
90
QARRVWKNYL
100
PAINGIVFLV
110
DCADHERLLE
120
SKEELDSLMT
130
DETVANVPIL
140
ILGNKIDRPE
150
AISEERLREM
160
FGLYGQTTGK
170
GSVSLKELNA
180
RPLEVFMCSV
190
LKRQGYGEGF
RWMAQYID
Gene Ontology
| Classification |
GO ID |
Description |
| Cellular Component |
GO:0030127 |
COPII vesicle coat |
| Cellular Component |
GO:0005829 |
cytosol |
| Cellular Component |
GO:0070971 |
endoplasmic reticulum exit site |
| Cellular Component |
GO:0005789 |
endoplasmic reticulum membrane |
| Cellular Component |
GO:0032580 |
Golgi cisterna membrane |
| Cellular Component |
GO:0005765 |
lysosomal membrane |
| Molecular Function |
GO:0140785 |
amino acid sensor activity |
| Molecular Function |
GO:0003925 |
G protein activity |
| Molecular Function |
GO:0005525 |
GTP binding |
| Molecular Function |
GO:0003924 |
GTPase activity |
| Molecular Function |
GO:0046872 |
metal ion binding |
| Biological Process |
GO:1990253 |
cellular response to leucine starvation |
| Biological Process |
GO:0048208 |
COPII vesicle coating |
| Biological Process |
GO:0090110 |
COPII-coated vesicle cargo loading |
| Biological Process |
GO:0006888 |
endoplasmic reticulum to Golgi vesicle-mediated transport |
| Biological Process |
GO:0006886 |
intracellular protein transport |
| Biological Process |
GO:0140353 |
lipid export from cell |
| Biological Process |
GO:0055088 |
lipid homeostasis |
| Biological Process |
GO:0042953 |
lipoprotein transport |
| Biological Process |
GO:0061024 |
membrane organization |
| Biological Process |
GO:1904262 |
negative regulation of TORC1 signaling |
| Biological Process |
GO:0003400 |
regulation of COPII vesicle coating |
| Biological Process |
GO:0032368 |
regulation of lipid transport |
| Biological Process |
GO:0016050 |
vesicle organization |
Reference
[1] Fan S, Zhou R, Wen H, Ye H, Ma S et al.. Global profiling of protein lactylome in porcine granulosa cells.. J Ovarian Res 18(1):177. 2025 Aug 8. PMID: 40781717.