NMR structure of the alpha-hemoglobin stabilizing protein: insights into conformational heterogeneity and binding.
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Santiveri CM, Perez-Canadillas JM, Vadivelu MK, Allen MD, Rutherford TJ, Watkins NA, Bycroft M
NMR structure of the alpha-hemoglobin stabilizing protein: insights into conformational heterogeneity and binding.
J Biol Chem. 2004 Aug 13;279(33):34963-70. Epub 2004 Jun 3.
- PubMed ID
- 15178680 [ View in PubMed]
- Abstract
The structure of alpha-hemoglobin stabilizing protein (AHSP), a molecular chaperone for free alpha-hemoglobin, has been determined using NMR spectroscopy. The protein native state shows conformational heterogeneity attributable to the isomerization of the peptide bond preceding a conserved proline residue. The two equally populated cis and trans forms both adopt an elongated antiparallel three alpha-helix bundle fold but display major differences in the loop between the first two helices and at the C terminus of helix 3. Proline to alanine single point mutation of the residue Pro-30 prevents the cis/trans isomerization. The structure of the P30A mutant is similar to the structure of the trans form of AHSP in the loop 1 region. Both the wild-type AHSP and the P30A mutant bind to alpha-hemoglobin, and the wild-type conformational heterogeneity is quenched upon complex formation, suggesting that just one conformation is the active form. Changes in chemical shift observed upon complex formation identify a binding interface comprising the C terminus of helix 1, the loop 1, and the N terminus of helix 2, with the exposed residues Phe-47 and Tyr-51 being attractive targets for molecular recognition. The characteristics of this interface suggest that AHSP binds at the intradimer alpha1beta1 interface in tetrameric HbA.