Analysis of the global architecture of hemoglobin A2 by heme binding studies and molecular modeling

• Published in: Journal of Protein Chemistry Vol. 17; no. 4; pp. 319 - 327
• Main Authors: Vasudevan, G, McDonald, M J
• Format: Journal Article
• Language: English
• Published: United States Springer Nature B.V 01.05.1998
• Subjects: Amino Acid Sequence; Amino acids; Binding; Computer Simulation; Heme; Heme - metabolism; Hemin; Hemoglobin; Hemoglobin A2 - chemistry; Hemoglobin A2 - metabolism; Humans; Kinetics; Modelling; Models, Molecular; Molecular biology; Molecular chains; Molecular modelling; Molecular Sequence Data; Potassium phosphate; Potassium phosphates; Protein Binding; Protein Conformation; Proteins
• ISSN: 0277-8033; 1572-3887; 1573-4943
• DOI: 10.1023/A:1022551131455

The kinetics of CNProto- and CNDeutero-hemin binding to apohemoglobin A2 was investigated in a stopped-flow device in 0.05 M potassium phosphate buffer, pH 7, at 10 degrees C. The overall kinetic profile exhibited multiple phases: Phases I-IV corresponding with heme insertion (8.5-13 x 10(7) M(-1) s(-1)), local structural rearrangement (0.21-0.23 s(-1)), global alphadelta structural event (0.071-0.098 s(-1)), and formation of the Fe-His bond (0.009-0.012 s(-1)), respectively. Kinetic differences observed between apohemoglobin A2 and apohemoglobin A (previously studied) prompted an analysis of the structures of beta and delta chains through molecular modeling. This revealed a structural repositioning of the residues not only at, but also distant from the site of the amino acid substitutions, specifically those involved in the heme contact and subunit interface. A significant global change was observed in the structure of the exon-coded 3 region and provided additional evidence for the designation of this as the subunit assembly domain.