About GTP-Binding Protein:
GTP-Binding Proteins, also known as SAR-1 or G proteins, are naturally occurring proteins found within the human body that act as transducin molecular switches that transmit extracellular signals to activate changes within the cell.
GTP-Binding Protein Structure
The GTP-Binding Proteins can be segregated into two classes, heterotrimeric G proteins and small GTPases with the latter being homologous to that of the Alpha subunit of heterotrimeric G protein. SAR-1 is an Arf family small GTPase and is additionally identified in plants and animals as well as humans. While included in the RAS 'superfamily' of small GTP-binding proteins, it is not closely related to other members of the RAS family, notably because it does not contain cysteine residues at the C terminus.
SAR-1 contains an NH2-terminal α1' helix domain The NH2-terminal residues (15-VLNFL-19) use the GDP activation to form the amphipathic helix (α1′). SAR-1, therefore, controls the assembly and fission of COPII vesicles
GTP-Binding Protein Mechanism
Guanine nucleotide-binding proteins that are heterodimeric membrane protein that are involved in mammalian cellular signaling pathways. They have Alpha, Beta, and Gamma subunits, with the former binding to GTP, which then disassociates itself with the Beta and Gamma subunits.
GTP-Binding Protein Function
G proteins can also bind by GDP, but the SAR-1 is a 21kDa GTP- binding protein that binds to the Sec-12p ER type II membrane protein to exchange the GDP to GTP. SAR-1 is located at chromosome 10 within humans. Its Entrez ID is 56681 while its Ensembl genome database project coding is ENSG00000079332. The gene is a member of the Human CCDS set.