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Direct observation of two distinct affinity conformations in the T state human deoxyhemoglobin
Author(s) -
Shibayama Naoya,
Saigo Satoshi
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02225-6
Subject(s) - chemistry , affinities , molecule , redistribution (election) , hemoglobin , crystallography , stereochemistry , biochemistry , organic chemistry , politics , political science , law
The main features of cooperative oxygenation of human hemoglobin have been described by assuming the equilibrium between two affinity conformations of the entire molecule, T and R. However, the molecular basis for explaining the wide variation in the O 2 affinities of the deoxy T state has remained obscure. We address this long‐standing issue by trapping the conformational states of deoxyhemoglobin molecules within wet porous transparent silicate sol‐gels. The equilibrium O 2 binding measurements of the encapsulated deoxyhemoglobin samples showed that deoxyhemoglobin free of anions coexists in two conformations that differ in O 2 affinity by 40 times or more, and addition of inositol hexaphosphate to this anion‐free deoxyhemoglobin brings about a very slow redistribution of these affinity conformations. These results are the first, direct demonstration of the existence of equilibrium between two (at least two) functionally distinguishable conformational states in the T state deoxyhemoglobin.