Fig. 1.

Clustalw2 alignment of T4-like phages’ portal clip regions. Amino acids in red could not be substituted in the phage and are conserved in T4-like phages. Amino acids in blue could be substituted and are not conserved in T4-like phages. The codons for the amino acids in pink were replaced by amber codons but could not be substituted by any other amino acid. Note D340 is the negatively charged residue at the tunnel entrance (see also Supplementary Fig. 1).