3qdr

Publication Abstract from PubMed

The Tol assembly of proteins is an interacting network of proteins located in the Eschericha coli cell envelope that transduces energy and contributes to cell integrity. TolA is central to this network linking the inner and outer membranes by interactions with TolQ, TolR, TolB and Pal. Group A colicins, such as ColA, parasitize the Tol network through interactions with TolA and/or TolB, to facilitate translocation through the cell envelope to reach their cytotoxic site of action. We have determined the first structure of the C-terminal domain of TolA (TolAIII) bound to an N-terminal ColA polypeptide (TA53-107). The interface region of the TA53-107-TolAIII complex consists of polar contacts linking residues R92 to R96 of ColA with residues L375-P380 of TolA which constitutes a beta-strand addition commonly seen in more promiscuous protein-protein contacts. The interface region also includes three cation-pi interactions (Y58-K368, Y90-K379, F94-K396) which have not been observed in any other colicin-Tol protein complex. Mutagenesis of the interface residues of ColA or TolA revealed that the effect on the interaction was cumulative; single mutations of either partner had no effect on ColA activity, whereas mutations of three or more residues significantly reduced ColA activity. Mutagenesis of the aromatic ring component of the cation-pi interacting residues showed Y58 of ColA to be essential for the stability of complex formation. TA53-107 binds on the opposite side of TolAIII to that used by g3p, ColN or TolB, illustrating the flexible nature of TolA as a periplasmic hub protein.

Structural evidence that colicin A binds to a novel binding site of TolA in the E.coli periplasm.,Li C, Zhang Y, Vankemmelbeke M, Hecht O, Aleanizy FS, Macdonald C, Moore GR, James R, Penfold CN J Biol Chem. 2012 Apr 9. PMID:22493500^[1]

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