GTP-binding protein SAR1b; GTP-binding protein B; GTBPB (SAR1B, SARA2, SARB)

Function

• role in transport from the endoplasmic reticulum to the Golgi
• activated by the guanine nucleotide exchange factor PREB
• involved in the selection of the protein cargo & the assembly of the COP2 coat complex
• binds PREB
• part of the COP2 coat complex
• binds to the cytoplasmic tails of target proteins in the endoplasmic reticulum (putative)

Structure

• homodimer
• belongs to the small GTPase superfamily, SAR1 family

Compartment

• endoplasmic reticulum membrane
• peripheral membrane protein (putative)
• Golgi, Golgi stack membrane
• associated with the endoplasmic reticulum & Golgi stacks, in particular in the juxta-nuclear Golgi region (putative)

Expression

• expressed in many tissues including small intestine, liver, muscle & brain

Pathology

• defects in SAR1B are the cause of chylomicron retention disease

More general terms

• guanine nucleotide regulatory protein (GNRP)
• prenyl protein
• guanosine triphosphatase (GTPase)

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=51128
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:51128
• OMIM: https://mirror.omim.org/entry/246700
• OMIM: https://mirror.omim.org/entry/607690
• UniProt: http://www.uniprot.org/uniprot/Q9Y6B6.html