Hemoglobin Einstein: Semisynthetic deletion in the B‐helix of the α‐chain

• Published in: Protein science Vol. 13; no. 5; pp. 1266 - 1275
• Main Authors: Srinivasulu, Sonati, Manjula, Belur N., Nagel, Ronald L., Tsai, Ching‐Hsuan, Ho, Chien, Prabhakaran, Muthuchidambaran, Acharya, Seetharama A.
• Format: Journal Article
• Language: English
• Published: Bristol Cold Spring Harbor Laboratory Press 01.05.2004
• Subjects: 1H‐NMR spectroscopy; DPG, 2,3 diphosphoglyceric acid, IHP, inositol hexaphosphate; DSS, dimethyl‐2‐silapentane 5‐sulfonate; HbA, human adult hemoglobin; HbCOA, carbon monoxy HbA; Hemoglobin A - chemistry; Hemoglobin A - isolation & purification; Hemoglobins, Abnormal - chemistry; Hemoglobins, Abnormal - metabolism; HEPES, N‐(2‐hydroxyethyl) piperazine ‐N‐(2‐ethane sulfonic acid); HMB, p‐hydroxymercuri benzoiate; IEF, iso‐electric focusing; kD, kilodaltons; L‐35, 3,5‐dichloro phenylureido‐phenoxy isobutyric acid; Magnetic Resonance Spectroscopy; Mass Spectrometry; Models, Molecular; molecular modeling; NMR, nuclear magnetic resonance; Oxygen - chemistry; Oxygen - metabolism; oxygen affinity; Peptides - chemical synthesis; Peptides - chemistry; Protein Structure, Secondary; Protein Subunits - chemistry; RP‐HPLC, reverse‐phase high‐performance liquid chromatography; Sequence Deletion; shortened B‐helix; ss‐Hb, semisynthetic hemoglobin; stuctural plasticity; subunit interfaces; thermodynamic stability; Thermodynamics
• ISSN: 0961-8368; 1469-896X
• DOI: 10.1110/ps.03567804

The influence of the deletion of the tetra peptide segment α23–26 of the B‐helix of the α‐chain of hemoglobin‐A on its assembly, structure, and functional properties has been investigated. The hemoglobin with the deletion, ss‐Hemoglobin‐Einstein, is readily assembled from semisynthetic α1–141 des23–26 globin and human βA‐chain. The deletion of α23–26 modulates the O2 affinity of hemoglobin in a buffer/allosteric effector specific fashion, but has little influence on the Bohr effect. The deletion has no influence on the thermodynamic stability of the α1β1 and the α1β2 interface. The semisynthetic hemoglobin exhibits normal intersubunit interactions at the α1β1 and α1β2 interfaces as reflected by 1H‐NMR spectroscopy. Molecular modeling studies of ss‐Hemoglobin‐Einstein suggest that the segment α28–35 is in a helical conformation, while the segment α19–22 is the nonhelical AB region. The shortened B‐helix conserves the interactions of α1β1 interface. The results demonstrate a high degree of plasticity in the hemoglobin structure that accommodates the deletion of α23–26 without perturbing its overall global conformation.