>cd00879 Sar1 Sar1 subfamily. Sar1 is an essential component of COPII vesicle coats involved in export of cargo from the ER. The GTPase activity of Sar1 functions as a molecular switch to control protein-protein and protein-lipid interactions that direct vesicle budding from the ER. Activation of the GDP to the GTP-bound form of Sar1 involves the membrane-associated guanine nucleotide exchange factor (GEF) Sec12. Sar1 is unlike all Ras superfamily GTPases that use either myristoyl or prenyl groups to direct membrane association and function, in that Sar1 lacks such modification. Instead, Sar1 contains a unique nine-amino-acid N-terminal extension. This extension contains an evolutionarily conserved cluster of bulky hydrophobic amino acids, referred to as the Sar1-N-terminal activation recruitment (STAR) motif. The STAR motif mediates the recruitment of Sar1 to ER membranes and facilitates its interaction with mammalian Sec12 GEF leading to activation.

Probab=90.39  E-value=0.22  Score=26.73  Aligned_cols=21  Identities=19%  Similarity=0.322  Sum_probs=17.9

Q ss_pred             CEEEEEECCCCCHHHHHHHHH
Q ss_conf             869999079865789999999
Q gi|254780640|r   51 HLTIVNGQNGYGKSSLSEAIE   71 (110)
Q Consensus        51 ~~~~i~G~Ng~GKStil~ai~   71 (110)
T Consensus        20 ~kIlilGld~aGKTTil~~l~   40 (190)
T cd00879          20 AKILFLGLDNAGKTTLLHMLK   40 (190)
T ss_pred             CEEEEEECCCCCHHHHHHHHH
T ss_conf             489999069998899999980