Forum 05/01/2003

“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!).

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