Hedrick P W, Whittam T S, Parham P
Institute of Molecular Evolutionary Genetics, Pennsylvania State University, University Park 16802.
Proc Natl Acad Sci U S A. 1991 Jul 1;88(13):5897-901. doi: 10.1073/pnas.88.13.5897.
The amino acid heterozygosities per site for HLA-A and -B loci are determined to be extremely high by combining population serotypic frequencies with amino acid sequences. For the 54 amino acid sites thought to have functional importance, the average heterozygosity per site is 0.301. Sixteen positions have heterozygosities greater than 0.5 at one or both loci and the frequencies of amino acids at a given position are very even, resulting in nearly the maximum heterozygosity possible. Furthermore, the high heterozygosity is concentrated in the peptide-interacting sites, whereas the sites that interact with the T-cell receptor have lower heterozygosity. Overall, these results indicate the importance of some form of balancing selection operating at HLA loci, maybe even at the individual amino acid level.
通过将群体血清型频率与氨基酸序列相结合，确定HLA - A和 - B位点每个位点的氨基酸杂合度极高。对于被认为具有功能重要性的54个氨基酸位点，每个位点的平均杂合度为0.301。16个位置在一个或两个位点的杂合度大于0.5，并且给定位置的氨基酸频率非常均匀，导致几乎达到可能的最大杂合度。此外，高杂合度集中在肽相互作用位点，而与T细胞受体相互作用的位点杂合度较低。总体而言，这些结果表明在HLA位点甚至可能在单个氨基酸水平上存在某种形式的平衡选择的重要性。
