Receptor specificity of the short tail fibres (gp12) of T-even type Escherichia coli phages

Abstract

Short tail fibres of T-even like phages are involved in host recognition. To determine the specificity of the fibres, the region containing gene 12 of phages T2, K3, and K3hx was cloned. The genes 11, 12, wac, and 13, coding for the baseplate outer wedge, short tail fibres, collar wishes, and a head completion component, respectively, were localized on the cloned fragments. Plasmid-encoded gene 12 could be expressed without helper phage. Efficient expression of gene 12 from T2 and K3hx made an extraction of protein 12 possible. Hybrid phages obtained by in vitro complementation, recombination analysis and protein 12 binding to host range mutant bacteria excluded a role of the short tail fibres from T2, K3 or K3hx in the recognition of outer membrane proteins. Binding patterns of protein 12 to different Escherichia coli lipopolysaccharide mutants and inhibition of binding of protein 12 by a monoclonal antibody against the core region of E. coli K12 lipopolysaccharide suggested that heptose residues are necessary for efficient binding. The binding site of the same monoclonal antibody is different from the short tail fibre binding site in an E. coli B strain suggesting different binding specificities of protein 12. Thus, the ability of different bacterial strains to inactivate phage could be related to differences in the binding specificity of the short tail fibres for the lipopolysaccharides of these bacteria.