5ck5

Publication Abstract from PubMed

G proteins of the Ras-family of small GTPases trace the evolution of eukaryotes. The earliest branching involves the closely related Arf, Sar1, and SRbeta GTPases associated with secretory membranes. SRbeta is an integral membrane component of the signal recognition particle (SRP) receptor that targets ribosome-nascent chain complexes to the ER. How SRbeta integrates into the regulation of SRP-dependent membrane protein biogenesis is not known. Here we show that SRbeta-GTP interacts with ribosomes only in presence of SRalpha and present crystal structures of SRbeta in complex with the SRX domain of SRalpha in the GTP-bound state at 3.2 A, and of GDP- and GDP.Mg2+-bound SRbeta at 1.9 A and 2.4 A, respectively. We define the GTPase switch cycle of SRbeta and identify specific differences to the Arf and Sar1 families with implications for GTPase regulation. Our data allow a better integration of SRbeta into the scheme of protein targeting.

Structure and Switch Cycle of SRbeta as Ancestral Eukaryotic GTPase Associated with Secretory Membranes.,Jadhav B, Wild K, Pool MR, Sinning I Structure. 2015 Aug 18. pii: S0969-2126(15)00292-0. doi:, 10.1016/j.str.2015.07.010. PMID:26299945^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.