Open and closed conformations of two SpoIIAA-like proteins (YP_749275.1 and YP_001095227.1) provide insights into membrane association and ligand binding.

ABSTRACT: The crystal structures of the proteins encoded by the YP_749275.1 and YP_001095227.1 genes from Shewanella frigidimarina and S. loihica, respectively, have been determined at 1.8 and 2.25?Å resolution, respectively. These proteins are members of a novel family of bacterial proteins that adopt the ?/? SpoIIAA-like fold found in STAS and CRAL-TRIO domains. Despite sharing 54% sequence identity, these two proteins adopt distinct conformations arising from different dispositions of their ?2 and ?3 helices. In the `open' conformation (YP_001095227.1), these helices are 15?Å apart, leading to the creation of a deep nonpolar cavity. In the `closed' structure (YP_749275.1), the helices partially unfold and rearrange, occluding the cavity and decreasing the solvent-exposed hydrophobic surface. These two complementary structures are reminiscent of the conformational switch in CRAL-TRIO carriers of hydrophobic compounds. It is suggested that both proteins may associate with the lipid bilayer in their `open' monomeric state by inserting their amphiphilic helices, ?2 and ?3, into the lipid bilayer. These bacterial proteins may function as carriers of nonpolar substances or as interfacially activated enzymes.

SUBMITTER: Kumar A 

PROVIDER: S-EPMC2954212 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature