Publication Abstract from PubMed
The remarkable ability of root effect haemoglobins to pump oxygen against high O2 gradients results from extreme, acid-induced reductions in O2 affinity and cooperativity. The long-sought mechanism for the root effect, revealed by the 2 angstrom crystal structure of the ligand-bound haemoglobin from Leiostomus xanthurus at pH 7.5, unexpectedly involves modulation of the R-state. Key residues strategically assemble positive-charge clusters across the allosteric beta1 beta2-interface in the R-state. At low pH, protonation of the beta N terminus and His 147(HC3)beta within these clusters is postulated to destabilize the R-state and promote the acid-triggered, allosteric R-->T switch with concomitant O2 release. Surprisingly, a set of residues specific to root effect haemoglobins recruit additional residues, conserved among most haemoglobins, to produce the root effect.
Structural basis for the root effect in haemoglobin.,Mylvaganam SE, Bonaventura C, Bonaventura J, Getzoff ED Nat Struct Biol. 1996 Mar;3(3):275-83. PMID:8605630[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
