BACTERIOPHAGE-T4 HOST-RANGE IS EXPANDED BY DUPLICATIONS OF A SMALL DOMAIN OF THE TAIL FIBER ADHESIN

The adsorption specificity of T4 is determined by the tip of the gene 37 tail fibers which bind to receptors on the bacterial surface. T4 in fects only Escherichia coli and closely related Shigella species, but rare host range mutants can be isolated that infect Yersinia pseudotub erculosis I, an evolutionally distant bacterium. Some of these mutatio ns result in amino acid residue substitutions in the C-terminal portio n of gene 37, but others involve unequal exchanges between a series of sequence motifs (I-lis boxes) in the same reg;ion. The duplication or mutational alteration of this segment apparently suffices for phage a dsorption to a Yersinia receptor. It is suggested that recombination b etween the His box sequences can generate diversity in phage host rang e by shuffling receptor recognition domains. (C) 1996 Academic Press L imited