title: Identification of new TAP2 alleles in gorilla: evolution of the locus within hominoids.
abstract: Transporters associated with antigen processing molecules (TAP1 and TAP2) mediate the transfer of cytosolic peptides into the lumen of the endoplasmic reticulum for association with newly synthesized class I molecules of the major histocompatibility complex. Previous molecular and functional analyses of rat and human TAP2 homologues indicated major differences in gene diversification patterns and selectivity of peptides transported. Therefore, in this study, we analyzed the alleles of the gorilla TAP2 locus to determine whether the pattern of diversification resembled that in either of those two species. Sequence analysis of the TAP2 cDNAs from gorilla Epstein-Barr virus-transformed B-cell lines revealed four alleles with a genetic distance of less than 1%. The nucleotide substitutions distinguishing the alleles are confined to the 3' half of the coding region and occur individually or within two small clusters of variability. Diversification of the locus appears to have resulted from point substitutions and recombinational events. Evolutionary-rate estimates for the TAP2 gene in gorilla and human closely approximate those observed for other hominoid genes. The amino acid polymorphisms within the gorilla molecules are distinct from those in the human homologues. The absence of ancestral polymorphisms suggests that gorilla and human TAP2 genes have not evolved in a trans-species fashion but rather have diversified since the divergence of the lineages.
authors.affiliation: Department of Immunology, Box 180, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA.
authors.forename: P T
authors.initials: PT
authors.lastname: Loflin
authors.forename: P R
authors.initials: PR
authors.lastname: Laud
authors.forename: D I
authors.initials: DI
authors.lastname: Watkins
authors.forename: D A
authors.initials: DA
authors.lastname: Lawlor
mesh_terms: D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics*; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002874:Chromosome Mapping; D006071:Gorilla gorilla / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D051381:Rats
chemical_list: D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; C489514:Tap2 protein, rat; C071692:TAP2 protein, human