The protein encoded by this gene is a small GTPase that acts as a homodimer. The encoded protein is activated by the guanine nucleotide exchange factor PREB and is involved in protein transport from the endoplasmic reticulum to the Golgi. This protein is part of the COPII coat complex. Defects in this gene are a cause of chylomicron retention disease (CMRD), also known as Anderson disease (ANDD). Two transcript variants encoding the same protein have been found for this gene. [provided by RefSeq, Mar 2010]
Function:
Involved in transport from the endoplasmic reticulum to the Golgi apparatus. Activated by the guanine nucleotide exchange factor PREB. Involved in the selection of the protein cargo and the assembly of the COPII coat complex.
Subunit:
Homodimer. Binds PREB. Part of the COPII coat complex. Binds to the cytoplasmic tails of target proteins in the endoplasmic reticulum (By similarity).
Subcellular Location:
Endoplasmic reticulum membrane. Golgi apparatus > Golgi stack membrane. Associated with the endoplasmic reticulum and Golgi stacks, in particular in the juxta-nuclear Golgi region.
Tissue Specificity:
Expressed in many tissues including small intestine, liver, muscle and brain.
DISEASE:
Defects in SAR1B are the cause of chylomicron retention disease (CMRD) [MIM:246700]; also known as Anderson disease (ANDD). CMRD is an autosomal recessive disorder of severe fat malabsorption associated with failure to thrive in infancy. The condition is characterized by deficiency of fat-soluble vitamins, low blood cholesterol levels, and a selective absence of chylomicrons from blood. Affected individuals accumulate chylomicron-like particles in membrane-bound compartments of enterocytes, which contain large cytosolic lipid droplets.
Similarity:
Belongs to the small GTPase superfamily. SAR1 family.
SWISS:
Q9Y6B6
Gene ID:
51128
Database links:
Entrez Gene: 51128 Human
Entrez Gene: 416314 Chicken
Entrez Gene: 515999 Cow
Entrez Gene: 66397 Mouse
Entrez Gene: 494017 Pig
Entrez Gene: 287276 Rat
Omim: 607690 Human
SwissProt: Q3T0T7 Cow
SwissProt: Q9Y6B6 Human
SwissProt: Q9CQC9 Mouse
SwissProt: Q5PYH3 Pig
SwissProt: Q5HZY2 Rat
Unigene: 432984 Human
Unigene: 196592 Mouse
Unigene: 36748 Rat
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