文章基本信息

标题：Noncooperativity of the αβ Dimer in the Reaction of Hemoglobin with Oxygen
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作者：J. A. Hewitt ; J. V. Kilmartin ; L. F. Ten Eyck 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1972
卷号：69
期号：1
页码：203-207
DOI：10.1073/pnas.69.1.203
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The theory that the [α]{beta} dimer is the functional unit of cooperativity in hemoglobin has been tested by determination of the oxygen equilibrium curve of stable deoxy dimers, obtained by the addition of 0.9 M MgCl2 to human des-Arg 141[α]-hemoglobin. Cooperativity was absent in this medium, but was regained on transfer of the hemoglobin to a dilute phosphate buffer, where tetramers reformed. X-ray analysis of crystals of oxy- and deoxy-des-Arg hemoglobins showed that the removal of Arg 141[α] would leave the structure of [α]{beta} dimers unchanged. Nonreactivity of the sulfhydryl groups at 112{beta} proved that the subunits in deoxy dimers form the same contact as in oxy dimers, namely [α]1{beta}1, and that no significant dissociation into free subunits occurs in 0.9 M MgCl2. The absorption spectrum of the deoxy dimers corresponded to the sum of the spectra of the free deoxy [α] and {beta} subunits, and was different from that of the deoxy tetramer, showing the constraining salt bridges formed by the C-terminal residues in the tetramer to be necessary for the spectral changes normally observed on association of the deoxy subunits.
关键词：human ; dissociation ; equilibrium ; sulfhydryl ; absorption ; x-ray analysis