Alignment of Ser-949 and His-950 in human MR with corresponding residues in other MRs, GRs and human AR and PR. Ser-949 in human MR is conserved in other MRs. The with the exception of skate GR, all other GRs contain a "signature" deletion of one amino acid, corresponding to Ser-949 in human MR. His-950 in human MR is conserved in human MR and other Old World primates. A glutamine is found in other MRs in land vertebrates and teleosts at this site. A corresponding lysine and glutamic acid and lysine are found in skate MR and hagfish CR, respectively. A corresponding glutamine is found in lamprey PR and CR.