Laud P R, Loflin P T, Jeevan A, Lawlor D A
Department of Immunology, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
Hum Immunol. 1996 Oct;50(2):91-102. doi: 10.1016/0198-8859(96)00137-1.
The transporter associated with antigen-processing (TAP) proteins are required for the transport of cytosolic peptides into the endoplasmic reticulum for assembly with class I major histocompatibility molecules. In the rat, allelic variants of the TAP genes impart specificity to the process of peptide transport. However, differential transport has yet to be demonstrated with the human molecules. TAP genes from humans and rodents have been studied thus far; analysis of another species more closely related to humans is necessary for a clearer understanding of the evolution of TAP genes. Three TAP1 alleles from four gorilla cell lines were characterized in this study. There is limited genetic distance at the locus, either within the gorilla (0.2%) or between the two hominoid species (0.8%). Nucleotide substitution analysis demonstrates that TAP1 and TAP2 are evolving at comparable rates under similar selection pressures. This pattern is in marked contrast to that observed for MHC class I genes of hominoids or rodents. Although there is limited evidence for trans-species evolution of the gorilla locus, the bulk of the diversification occurred after speciation as evidenced by a lack of shared amino acid polymorphism with human homologues. An evolutionary scheme predicts that the ancestral hominoid TAP1 molecule most closely resembled the human TAP1*02011.
抗原加工相关转运体（TAP）蛋白是将胞质肽转运至内质网以与I类主要组织相容性分子组装所必需的。在大鼠中，TAP基因的等位基因变体赋予了肽转运过程特异性。然而，人类分子的差异转运尚未得到证实。迄今为止，已经对人类和啮齿动物的TAP基因进行了研究；为了更清楚地了解TAP基因的进化，有必要分析与人类关系更密切的另一个物种。本研究对来自四个大猩猩细胞系的三个TAP1等位基因进行了表征。在该位点，大猩猩内部（0.2%）或两个类人猿物种之间（0.8%）的遗传距离有限。核苷酸取代分析表明，在相似的选择压力下，TAP1和TAP2以相当的速率进化。这种模式与类人猿或啮齿动物的MHC I类基因所观察到的模式形成鲜明对比。尽管大猩猩位点的跨物种进化证据有限，但大部分多样化发生在物种形成之后，这一点从与人类同源物缺乏共享氨基酸多态性可以看出。一个进化方案预测，原始类人猿TAP1分子最类似于人类TAP1*02011。
