6mic

Publication Abstract from PubMed

Virulent strains of the bacterial pathogen Vibrio cholerae cause the diarrheal disease cholera by releasing cholera toxin into the small intestine. V. cholerae acquired its cholera toxin genes by lysogenic infection with the filamentous bacteriophage CTXphi. CTXphi uses its minor coat protein pIII, located in multiple copies at the phage tip, to bind to the V. cholerae toxin-coregulated pilus (TCP). However, the molecular details of this interaction and the mechanism of phage internalization are not well-understood. The TCP filament is a polymer of major pilins, TcpA, and one or more minor pilin, TcpB. TCP are retractile, with both retraction and assembly initiated by TcpB. Consistent with these roles in pilus dynamics, we hypothesized that TcpB controls both binding and internalization of CTXphi. To test this hypothesis, we determined the crystal structure of the C-terminal half of TcpB and characterized its interactions with CTXphi pIII. We show that TcpB is a homotrimer in its crystallographic form as well as in solution and is present in multiple copies at the pilus tip, which likely facilitates polyvalent binding to pIII proteins at the phage tip. We further show that recombinant forms of TcpB and pIII interact in vitro, and both TcpB and anti-TcpB antibodies block CTXphi infection of V. cholerae Finally, we show that CTXphi uptake requires TcpB-mediated retraction. Our data support a model whereby CTXphi and TCP bind in a tip-to-tip orientation, allowing the phage to be drawn into the V. cholerae periplasm as an extension of the pilus filament.

The Vibrio cholerae minor pilin TcpB mediates uptake of the cholera toxin phage CTXphi.,Gutierrez-Rodarte M, Kolappan S, Burrell BA, Craig L J Biol Chem. 2019 Oct 25;294(43):15698-15710. doi: 10.1074/jbc.RA119.009980. Epub, 2019 Aug 30. PMID:31471320^[1]

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