New insights into the molecular mechanism of the Rab GTPase Sec4p activation.

ABSTRACT:

Background

Sec4p is a small monomeric Ras-related GTP-binding protein (23 kDa) that regulates polarized exocytosis in S. cerevisiae. In this study we examine the structural effects of a conserved serine residue in the P-loop corresponding to G12 in Ras.

Results

We show that the Sec4p residue serine 29 forms a hydrogen bond with the nucleotide. Mutations of this residue have a different impact than equivalent mutations in Ras and can form stable associations with the exchange factor allowing us to elucidate the structure of a complex of Sec4p bound to the exchange factor Sec2p representing an early stage of the exchange reaction.

Conclusions

Our structural investigation of the Sec4p-Sec2p complex reveals the role of the Sec2p coiled-coil domain in facilitating the fast

SUBMITTER: Rinaldi FC 

PROVIDER: S-EPMC4531439 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature