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Structure and properties of a natural competence-associated pilin suggest a unique pilus tip-associated DNA receptor

DOI: 10.1128/mBio.00614-19 DOI Help

Authors: Mohd Zulkifli Salleh (The University of Manchester) , Vijaykumar Karuppiah (The University of Manchester) , Matthew Snee (The University of Manchester) , Angela Thistlethwaite (The University of Manchester) , Colin W. Levy (The University of Manchester) , David Knight (The University of Manchester) , Jeremy P. Derrick (The University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Mbio , VOL 10 , PAGES e00614-19

State: Published (Approved)
Published: June 2019
Diamond Proposal Number(s): 8997

Open Access Open Access

Abstract: Natural competence is the term used to describe the uptake of “naked” extracellular DNA by bacteria; it plays a significant role in horizontal genetic exchange. It is associated with type IV pili, and specialized competence pili mediate DNA uptake. Here, we show that the crystal structure of a competence-associated protein from Thermus thermophilus, ComZ, consists of a type II secretion pseudopilin-like domain, with a large β-solenoid domain inserted into the β-sheet of the pilin-like fold. ComZ binds with high affinity to another competence-associated pilin, PilA2, which lies adjacent to the comZ gene in the genome. The crystal structure of PilA2 revealed a similar type II secretion pseudopilin-like fold, with a small subdomain; docking simulations predicted that PilA2 binds between the pseudopilin-like and β-solenoid domains of ComZ. Electrophoretic shift analysis and DNase protection studies were used to show that ComZ alone and the ComZ/PilA2 complex are able to bind DNA. Protection against reductive dimethylation was used in combination with mass spectrometry and site-directed mutagenesis to identify two lysine residues in ComZ which are involved in DNA binding. They are located between the two domains in ComZ, on the opposite side from the predicted PilA2 binding site. These results suggest a model in which PilA2 assists ComZ in forming the competence pilus tip and DNA binds to the side of the fiber. The results demonstrate how a type IV pilin can be adapted to a specific function by domain insertion and provide the first structural insights into a tip-located competence pilin.

Journal Keywords: X-ray crystallography; genetic competence; natural transformation systems; pilus assembly; surface receptor

Subject Areas: Biology and Bio-materials

Instruments: I02-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength)