Tucker P W, Phillips S E, Perutz M F, Houtchens R, Caughey W S
Proc Natl Acad Sci U S A. 1978 Mar;75(3):1076-80. doi: 10.1073/pnas.75.3.1076.
In hemoglobin Zürich the side chain of the distal arginine attaches itself to the propionate of the heme, leaving the heme pocket wide open, allowing sulfanilamides easy access to the iron, and doubling the partition coefficient between CO and O2. The replacement of the distal valine by alanine in hemoglobin Sydney leaves a large gap inside the heme pocket, which is partly filled by a water molecule bonded to the distal histidine. Hemoglobin Sydney has the same partition coefficient between CO and O2 as hemoglobin A. Replacement of the distal histidine increases the stretching frequency of CO linked to the beta heme by 6 cm-1, but replacement of the distal valine increases it by only 3 cm-1, but replacement of the distal histidine leaves the O-O stretching frequency unchanged.
在苏黎世血红蛋白中,远端精氨酸的侧链与血红素的丙酸酯相连,使血红素口袋大开,让磺胺类药物易于接近铁,并使一氧化碳和氧气之间的分配系数加倍。在悉尼血红蛋白中,远端缬氨酸被丙氨酸取代,在血红素口袋内留下一个大空隙,部分被与远端组氨酸结合的水分子填充。悉尼血红蛋白在一氧化碳和氧气之间的分配系数与血红蛋白A相同。远端组氨酸的取代使与β-血红素相连的一氧化碳的伸缩频率增加6厘米-1,但远端缬氨酸的取代仅使其增加3厘米-1,而远端组氨酸的取代使氧-氧伸缩频率不变。