Structural basis for the root effect in haemoglobin
- PMID: 8605630
- DOI: 10.1038/nsb0396-275
Structural basis for the root effect in haemoglobin
Abstract
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.
Comment in
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Cause of the root effect in fish haemoglobins.Nat Struct Biol. 1996 Mar;3(3):211-2. doi: 10.1038/nsb0396-211. Nat Struct Biol. 1996. PMID: 8605618
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