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FLASH GENE
Symbol SAR1B contributors: mct/npt - updated : 31-01-2018
HGNC name SAR1 gene homolog B (S. cerevisiae)
HGNC id 10535
PROTEIN
PHYSICAL PROPERTIES
STRUCTURE
motifs/domains
  • N-terminal amphipathic alpha helix
  • mono polymer homomer , dimer
    HOMOLOGY
    intraspecies paralog to SAR1A
    Homologene
    FAMILY
  • small GTPase superfamily
  • SAR1 family
  • CATEGORY transport carrier
    SUBCELLULAR LOCALIZATION     intracellular
    intracellular,cytoplasm,organelle,membrane
    intracellular,cytoplasm,organelle,endoplasmic reticulum
    intracellular,cytoplasm,organelle,Golgi
    intracellular,cytoplasm,cytosolic
    text peripheral membrane protein associated with the endoplasmic reticulum and golgi stacks, in particular in the juxta-nuclear golgi region
    basic FUNCTION
  • involved in the intracellular trafficking of proteins in COP-coated vesicles
  • involved in the vesicular COPII dependent transport of proteins from the endoplasmic reticulum (ER) to the Golgi apparatus (Silvain 2008)
  • playing an important role in processes involving erythroid cell proliferation and differentiation
  • plays a significant role in the assembly, organization, and function of the coat protein complex II, a critical complex for the transport of proteins from the endoplasmic reticulum to the Golgi
  • SAR1A and SAR1B proteins lower membrane rigidity at low concentrations, and at high concentrations, increase membrane rigidity
  • SAR1A, SAR1B GTPase coordinates the assembly of coat protein complex-II (COPII) at specific sites of the endoplasmic reticulum (ER)
  • SAR1A antagonizes the lipoprotein secretion-promoting activity of SAR1B, both isoforms modulate the expression of genes encoding cholesterol biosynthetic enzymes and the synthesis of cholesterol
  • SAR1B promotes the secretion of hepatic lipids but also adds regulation of cholesterol synthesis to SAR1B's repertoire of transport functions
  • importance of SAR1B in organs involved in lipid transport and/or calcium trafficking such as the liver, intestine, skeletal muscle and heart
  • SAR1A, SAR1B dimerization is responsible for the formation of constrictive membrane curvature
  • SAR1B GTPase is a key component of Coat protein complex II (COPII)-coated vesicles that bud from the endoplasmic reticulum to export newly synthesized proteins
  • SAR1B overexpression contributes to regulation of Cholestérol (CHOL) transport and metabolism by facilitating rapid uptake and transport of CHOL
  • Sar1B GTPase is one of the critical proteins governing chylomicron secretion by the small intestine
  • CELLULAR PROCESS
    PHYSIOLOGICAL PROCESS
    PATHWAY
    metabolism
    signaling
    a component
    INTERACTION
    DNA
    RNA
    small molecule nucleotide,
  • Mg2+
  • GTP
  • protein
  • may promote intestinal lipid transport with the involvement of the coat protein complex II network and the processing of SREBF1
  • promotes hepatic apolipoprotein (apo) B lipoprotein secretion and this promoting activity is coordinated with the processes regulating APOB expression and the transfer of triglycerides/cholesterol moieties onto this large lipid transport protein
  • cell & other
    REGULATION
    Other is regulated in a time- and concentration-dependent manner by dietary lipids, suggesting an adaptation to alimentary lipid flux
    ASSOCIATED DISORDERS
    corresponding disease(s) CMRD
    Susceptibility
    Variant & Polymorphism
    Candidate gene
    Marker
    Therapy target
    ANIMAL & CELL MODELS
  • Sar1b transgenic mice displayed higher gene expression in the liver, ileum, jejunum, proximal and distal colon compared to wild-type mice