A bacteriophage capsid protein is an inhibitor of a conserved transcription terminator of various bacterial pathogens

Abstract

Rho is a hexameric molecular motor that functions as a conserved transcription terminator in majority of the bacterial species, which is a potential drug target. Psu is a bacteriophage P4 capsid protein that inhibits E.coli Rho by obstructing its ATPase and translocase activities. Here, we explored the anti-Rho activity of Psu for the Rho proteins from different pathogens. Sequence alignment and homology modelling of Rho proteins from pathogenic bacteria revealed the conserved nature of the Psu-interacting regions in all these proteins. We chose Rho proteins from various pathogens like, Mycobacterium smegmatis, Mycobacterium bovis, Mycobacterium tuberculosis, Xanthomonas campestris, Xanthomonas oryzae, Corynebacterium glutamicum, Vibrio cholerae, Salmonella enterica and Pseudomonas syringae. The purified recombinant Rho proteins of these organisms showed variable rates of ATP hydrolysis on the poly (rC) as substrate and were capable of releasing RNA from the E. coli transcription elongation complexes. Psu was capable of inhibiting these two functions of all these Rho proteins. In vivo pull down assays revealed direct binding of Psu with many of these Rho proteins. In vivo expression of psu induced killing of M. smegmatis, M. bovis, X.campestris and S.enterica, indicating Psu-induced inhibition of Rho proteins of these strains under physiological conditions. We propose that the “universal” inhibitory function of the Psu protein against the Rho proteins from both the gram-negative and gram-positive bacteria could be useful for designing peptides having anti-microbial functions, and these peptides could be a part of synergistic antibiotic treatment of the pathogens through compromising the Rho functions.