Open AccessStructure of deoxyhemoglobin Cowtown [His HC3(146) beta----Leu]: origin of the alkaline Bohr effect and electrostatic interactions in hemoglobin.
Author(s) -
M. F. Perutz,
G. Fermi,
T. B. Shih
Publication year - 1984
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.81.15.4781
Subject(s) - bohr effect , salt bridge , chemistry , side chain , hemoglobin , histidine , salt (chemistry) , stereochemistry , alpha chain , crystallography , chain (unit) , beta (programming language) , amino acid , biochemistry , organic chemistry , physics , receptor , astronomy , mutant , oxygen–haemoglobin dissociation curve , gene , polymer , computer science , programming language
Hemoglobin Cowtown [His HC3(146)-beta----Leu] exhibits high oxygen affinity and a halved alkaline Bohr effect. X-ray analysis shows the COOH-terminal leucine to be in equilibrium between two positions: one with the salt bridge between the terminal carboxyl and Lys C5(40)alpha intact and the leucyl side chain leaning against main chain atoms of helices F and FG and the other with the terminal salt bridge broken and the leucyl side chain touching Pro C2(37)alpha. Structural changes are confined to the immediate neighborhood of the COOH terminus, showing the halving of the alkaline Bohr effect to be due directly to the loss of the histidine, without significant contributions from changes in pK values of other ionizable groups due to structural changes elsewhere.