Abstract
The interaction between a bacteriophage and its host is mediated by the phage’s receptor binding protein (RBP). Despite its fundamental role in governing phage activity and host range, molecular rules of RBP function remain a mystery. Here, we systematically dissect the functional role of every residue in the tip domain of T7 phage RBP using a high-throughput, locus-specific, phage engineering method. We find that function-enhancing mutations are concentrated around outward-facing loops suggesting directionality and orientational-bias in receptor engagement. These mutations are host-specific, indicating adaptation to individual hosts and highlighting a tradeoff between activity and host range. We discover gain-of-function variants effective against resistant strains and host-constricting variants that selectively eliminate certain hosts. We demonstrate therapeutic utility against uropathogenic E. coli by engineering a highly active T7 to avert emergence of spontaneous resistance of the pathogen. Our approach is generalizable to other phages and will enable the design of programmable phages.
Competing Interest Statement
P.H and S.R have filed a provisional patent application on this technology. S.R is on the scientific advisory board of MAP/PATH LLC.
