Imai K, Shih D T, Tame J, Nagai K, Miyazaki G
Department of Physicochemical Physiology, Medical School, Osaka University, Japan.
Protein Seq Data Anal. 1989 Feb;2(2):81-6.
Compiled data for more than 440 natural human hemoglobin mutants with single amino acid substitutions indicate that molecular properties (oxygen binding, structural stability, ease of autooxidization, etc.) of more than half of them are altered in some way and that the mode of alteration is closely related to the region within the hemoglobin molecule in which the substitution takes place. The present study gives a quantitative basis for the correlations. By means of protein engineering, including site-directed mutagenesis, several artificial mutants of human hemoglobin were prepared and their oxygen binding properties were studied to investigate the functional consequences of the amino acid substitutions which have not yet been isolated in natural mutants. These artificial mutants gave straight-forward information regarding the major factors regulating the oxygen affinity of heme and the identification of a Bohr group in the alpha chain. On the other hand the mutants, which were designed to test some hypotheses for the molecular evolution in hemoglobin, did not necessarily give the results predicted from accumulated structure-function data obtained from the study of natural mutants and X-ray crystallographic analyses.
对440多种具有单个氨基酸替换的天然人类血红蛋白突变体的汇总数据表明，其中一半以上的分子特性（氧结合、结构稳定性、自氧化难易程度等）以某种方式发生了改变，并且改变模式与血红蛋白分子内发生替换的区域密切相关。本研究为这些相关性提供了定量依据。通过蛋白质工程，包括定点诱变，制备了几种人工人类血红蛋白突变体，并研究了它们的氧结合特性，以研究在天然突变体中尚未分离出的氨基酸替换的功能后果。这些人工突变体提供了关于调节血红素氧亲和力的主要因素以及α链中一个玻尔基团的鉴定的直接信息。另一方面，为检验血红蛋白分子进化的一些假设而设计的突变体，并不一定能得出从天然突变体研究和X射线晶体学分析获得的累积结构-功能数据所预测的结果。
