POLYMERIZATION OF HEMOGLOBIN-S - QUINARY INTERACTIONS OF GLU-43(BETA)

Hemoglobin S (HbS) Hoshida and three substituted forms of HbS Hoshida (the substituents being on the amide nitrogen of Gln-43(beta)) have be en prepared by the amidation of Glu-43(beta) of HbS with ammonia, meth ylamine, glycine ethyl ester, and galactosamine. The O-2 affinity of H bS is increased slightly on amidation of Glu-43(beta). All the four am idated derivatives exhibited nearly the same oxygen affinity. On the o ther hand, the influence of amidation on the solubility exhibits some sensitivity to the chemical nature of the substituent on the Gln-43(be ta). The solubility of HbS Hoshida (a case with no substitution on Gln -43(beta)), and the methyl-substituted derivatives are about 33 and 36 % higher than that of HbS. The solubility of the HbS modified with the glycine ethyl ester or galactosamine is increased to 41 and 47%, resp ectively. The first derivative UV spectra of HbS Hoshida and its methy l derivative reflect very little perturbations in their alpha(1) beta( 2) interface as compared with that of HbS, whereas the amidated deriva tives with larger substituents on Gln-43(beta) reflected noticeable di fferences. Thus, the increase in the solubility and the oxygen affinit y of HbS on the amidation of Glu-43(beta) is primarily a consequence o f the loss of the negative charge at 43(beta), a residue proximal to t he alpha 1 beta(2) interface. The copolymerization studies of amidated HbS with HbA and HbS with amidated HbA demonstrate that cis Glu-43(be ta) is the ''active'' residue. This assignment is discrepant with the earlier implication of a trans configuration for this residue in the p olymer (Edelstein, S. J. (1981) J. Mol. Biol. 150, 557-575). However, it is consistent with the solution studies of Nagel ct al. (Nagel, R. L., Bookchin, R. M., Johnson, J., Labie, D., Wajcman, H., Isaac-Sodeye , W. A., Honig, G. R., Schiliro, G., Crookstan, J. H., and Matsutomo, K. (1979) Proc. Not. Acad. Sci. U. S. A. 76, 670-672) and McCurdy ct a l. (McCurdy, P. R., Lorkin, P. A., Casey, R., Lehmann, H., Uddin, D. E ., and Dickson, L. G. (1974) Am. J. Med. 57, 665-760).