title: Structure of the altitude adapted hemoglobin of guinea pig in the R2-state.
abstract: BACKGROUND
  Guinea pigs are considered to be genetically adapted to a high altitude environment based on the consistent finding of a high oxygen affinity of their blood.
  
  
  RESULTS
  The crystal structure of guinea pig hemoglobin at 1.8 A resolution suggests that the increased oxygen affinity of guinea pig hemoglobin can be explained by two factors, namely a decreased stability of the T-state and an increased stability of the R2-state. The destabilization of the T-state can be related to the substitution of a highly conserved proline (P44) to histidine (H44) in the alpha-subunit, which causes a steric hindrance with H97 of the beta-subunit in the switch region. The stabilization of the R2-state is caused by two additional salt bridges at the beta1/beta2 interface.
  
  
  CONCLUSIONS
  Both factors together are supposed to serve to shift the equilibrium between the conformational states towards the high affinity relaxed states resulting in an increased oxygen affinity.
authors.affiliation: Institut für Molekulare Biophysik, Johannes Gutenberg Universität, Mainz, Germany.
authors.forename: Bruno
authors.initials: B
authors.lastname: Pairet
authors.forename: Elmar
authors.initials: E
authors.lastname: Jaenicke
mesh_terms: D000222:Adaptation, Physiological; D000531:Altitude; D000818:Animals; D018360:Crystallography, X-Ray; D006168:Guinea Pigs / Q000502:physiology*; D006454:Hemoglobins / Q000737:chemistry*; D008958:Models, Molecular; D055550:Protein Stability; D020836:Protein Structure, Quaternary
chemical_list: D006454:Hemoglobins
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