FIG. 3.

Amino acid sequence alignments of the central portion of gene 23 of T4-type phages. For T4, the translation of the nucleotide sequence between codons 115 and 302 is shown. The protein sequences of the other 17 phages were aligned with the T4 sequence using the ClustalX program (36). Amino acid motifs common to all of the T4-type subgroups are indicated by a black background. Amino acid motifs that are well conserved within a T4-type subgroup phage are indicated by a color code (red, T-evens; green, pseudoT-evens; and blue, schizoT-evens). Sequences shown with a white background were not well conserved within their subgroup. The following groups of aa were considered equivalent in this presentation (D = N, E = Q, K = R, F = Y = W, and L = I = V = M). A dash indicates a space was inserted in the sequence to preserve the alignment. An ambiguity in the nucleotide sequence is indicated by an X for the corresponding codon. The coordinates of the T4 gene 23 aa sequence are shown at the extremities of the comparison in bold characters.