Alignment of C. pneumoniae AaxB sequence with orthologs from C. muridarum Nigg, C. trachomatis L2/434, D/UW-3, B/Jali, and A/HAR-13. Conserved amino acid residues are indicated by dots, while differences in the chlamydial sequences are indicated by lower-case symbols. The bottom row of the alignment shows an ancestral sequence for the C. trachomatis aaxB genes that was predicted using the codeml program, as described in the text. The ochre128 nonsense codon in the C. trachomatis L2/434 sequence is indicated by an asterisk, and the column of corresponding amino acids is colored red. The column of residues corresponding to Arg and Gly115 is also colored red. Sequence accession numbers are listed in Table 5.