Abstract
Equilibrium constants for the binding of ethyl (EIC), n-butyl (BIC), p-toluenesulphonylmethyl (TMIC) and 2,6-dimethylphenyl isocyanides (DIMPI) to an imidazole-haem complex in toluene and aqueous detergent micelle solutions were determined. In contrast to an earlier study, which indicated that the large affinities of myoglobin for binding DIMPI and 2,6-diethylphenylisocyanide (DEPI) relative to EIC were due to an electronic effect, the present study shows a similarity in binding constants for EIC, BIC, and DIMPI to the imidazole-haem complex in toluene, suggesting no such electronic effect is present. The measured hydrophobic effect (KDIMPI/KEIC = 11) cannot account for the large binding constant reported for DIMPI relative to the binding of EIC to myoglobin. Based on the results of these model studies, the equilibrium binding constant for DIMPI to myoglobin has been re-measured and the standard free energy of binding has been analysed by a more recent method.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- AINSWORTH S., GIBSON Q. H., ROUGHTON F. J. The kinetics of sheep haemoglobin with isocyanides. Proc R Soc Lond B Biol Sci. 1960 Jun 14;152:331–345. doi: 10.1098/rspb.1960.0042. [DOI] [PubMed] [Google Scholar]
- Brunori M., Talbot B., Colosimo A., Antonini E., Wyman J. Studies on the reaction of isocyanides with haemproteins. II. Binding to normal and modified human haemoglobins. J Mol Biol. 1972 Apr 14;65(3):423–434. doi: 10.1016/0022-2836(72)90199-4. [DOI] [PubMed] [Google Scholar]
- Mims M. P., Porras A. G., Olson J. S., Noble R. W., Peterson J. A. Ligand binding to heme proteins. An evaluation of distal effects. J Biol Chem. 1983 Dec 10;258(23):14219–14232. [PubMed] [Google Scholar]
- Reisberg P. I., Olson J. S. Equilibrium binding of alkyl isocyanides to human hemoglobin. J Biol Chem. 1980 May 10;255(9):4144–4130. [PubMed] [Google Scholar]
- Reisberg P. I., Olson J. S. Kinetic and cooperative mechanisms of ligand binding to hemoglobin. J Biol Chem. 1980 May 10;255(9):4159–4169. [PubMed] [Google Scholar]
- Reisberg P. I., Olson J. S. Rates of isonitrile binding to the isolated alpha and beta subunits of human hemoglobin. J Biol Chem. 1980 May 10;255(9):4151–4158. [PubMed] [Google Scholar]
- Romberg R. W., Kassner R. J. Effects of solvent on the absorption maxima of five-coordinate heme complexes and carbon monoxide-heme complexes as models for the differential spectral properties of hemoglobins and myoglobins. Biochemistry. 1982 Mar 2;21(5):880–886. doi: 10.1021/bi00534a011. [DOI] [PubMed] [Google Scholar]
- ST GEORGE R. C. C., PAULING L. The combining power of hemoglobin for alkyl isocyanides, and the nature of the heme-heme interactions in hemoglobin. Science. 1951 Dec 14;114(2972):629–634. doi: 10.1126/science.114.2972.629. [DOI] [PubMed] [Google Scholar]
- Wood M. A., Dickinson K., Willey G. R., Dodd G. H. Binding of aromatic isonitriles to haemoglobin and myoglobin. Biochem J. 1987 Nov 1;247(3):675–678. doi: 10.1042/bj2470675. [DOI] [PMC free article] [PubMed] [Google Scholar]