NMR Structure of the α-Hemoglobin Stabilizing Protein

• Published in: The Journal of biological chemistry Vol. 279; no. 33; p. 34963
• Main Authors: Clara M. Santiveri, José Manuel Pérez-Cañadillas, Murali K. Vadivelu, Mark D. Allen, Trevor J. Rutherford, Nicholas A. Watkins, Mark Bycroft
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 13.08.2004
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M405016200

The structure of α-hemoglobin stabilizing protein (AHSP), a molecular chaperone for free α-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 α-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 α-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 α 1 β 1 interface in tetrameric HbA.