“Identification of a putative periplasmic transporter protein from Vibrio”
Lisa Craig, Research Associate – Tainer Getzoff Lab, The Scripps Research Institute, La Jolla, CA
I have identified a striking tetrameric complex from negative stains of Vibrio cholerae cell lysates. The complex is comprised of four globular domains arranged at the four corners of a square. Thin connectors can be observed between the subunits along the sides of the squares. They measure ~11 nm across and the globular domains are 3-4 nm in diameter. In some cases a side view is observed suggesting that the complexes are in fact cubic. Using mass spectrometry on the major Coomassie-stained bands in the cell lysate the tetrameric complex has been tentatively identified as a 36 kDa “immunogenic protein”. This protein shares sequence homology with a TRAP transporter, a “tripartite ATPase-independent periplasmic transporter that shuttles C4-dicarboxylates (malate, succinate and fumarate) across the periplasm. This complex is abundant in the V. cell extracts and has also been observed in E. coli extracts. I will discuss these very preliminary data and my plans for solving its structure (provided it hasn’t already been solved!).