Allosteric intermediates indicate R2 is the liganded hemoglobin end state.
Hemoglobin has been a long-standing paradigm for understanding protein allostery. Here, the x-ray structures of two chemically crosslinked, fully liganded hemoglobins, alpha2beta82CA82beta and alpha2beta82ND82beta, are described at 2.3 A and 2.6 A resolution, respectively. Strikingly, these crosslinked hemoglobins assume intermediate conformations that lie between those of R and the controversial liganded hemoglobin state R2 rather than between R and T. Thus, these structures support only a T left and right arrow R left and right arrow R2 allosteric pathway and underscore the physiological importance of the R2 conformation.
Schumacher, MA; Zheleznova, EE; Poundstone, KS; Kluger, R; Jones, RT; Brennan, RG
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