STRUCTURAL-ANALYSIS OF THE RH-LIKE BLOOD-GROUP GENE-PRODUCTS IN NONHUMAN-PRIMATES

Rh-related transcripts present in bone marrow samples from several spe cies of nonhuman primates (chimpanzee, gorilla, gibbon, crab-eating ma caque) have been amplified by RT-polymerase chain reaction using prime rs deduced from the sequence of human RH genes. Nucleotide sequence an alysis of the nonhuman transcripts revealed a high degree of similarit y to human blood group Ph sequences, suggesting a great conservation o f the RH genes throughout evolution. Full-length transcripts, potentia lly encoding 417 amino acid long proteins homologous to Ph polypeptide s, were characterized, as well as mRNA isoforms which harbored nucleot ide deletions or insertions and potentially encode truncated proteins. Proteins of 30-40000 M(r), immunologically related to human Rh protei ns, were detected by western blot analysis with antipeptide antibodies , indicating that Rh-like transcripts are translated into membrane pro teins. Comparison of human and nonhuman protein sequences was pivotal in clarifying the molecular basis of the blood group C/c polymorphism, showing that only the Pro103Ser substitution was correlated with C/c polymorphism. In addition, it was shown that a proline residue at posi tion 102 was critical in the expression of C and c epitopes, most like ly by providing an appropriate conformation of Ph polypeptides. From t hese data a phylogenetic reconstruction of the RH locus evolution has been calculated from which an unrooted phylogenetic tree could be prop osed, indicating that African ape Rh-Like genes would be closer to the human RhD gene than to the human RhCE gene.