PMID: 2500435Jul 5, 1989Paper

Structure-function relationships in hemoglobin Kariya, Lys-40(C5) alpha----Glu, with high oxygen affinity. Functional role of the salt bridge between Lys-40 alpha and the beta chain COOH terminus.

The Journal of Biological Chemistry
K ImaiK Harano

Abstract

The epsilon-amino group of Lys-40 alpha forms a salt bridge with the alpha-carboxyl group of beta chain in deoxyhemoglobin and is considered to impose a constraint upon hemoglobin tetramer, stabilizing the T quaternary structure. Hb Kariya, in which Lys-40 alpha is replaced by Glu, provides a unique opportunity to investigate the functional role of this salt bridge. Hb Kariya showed oxygen binding properties characterized by a high affinity, diminished cooperativity, a reduced alkaline Bohr effect, and a decreased effect of phosphates upon oxygen affinity. In deoxyHb Kariya the reactivity of the sulfhydryl groups of cysteins-93 beta with 4,4'-dipyridine disulfide was profoundly enhanced, being comparable to that for normal oxyhemoglobin (oxyHb A). The Soret band spectra, UV derivative spectra, and UV oxyminus-deoxy difference spectra indicated that oxyHb Kariya assumes a quaternary structure similar to that of oxyHb A whereas the T structure of deoxyHb Kariya is destabilized, and Hb Kariya remains predominantly in the R state upon deoxygenation. Resonance Raman scattering by deoxyHb Kariya showed that the Fe-N epsilon(proximal His) bond is less stretched than that of deoxyHb A. These experimental results provide structural basi...Continue Reading

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