| Autor: |
K, Imai, K, Fushitani, G, Miyazaki, K, Ishimori, T, Kitagawa, Y, Wada, H, Morimoto, I, Morishima, D T, Shih, J, Tame |
| Rok vydání: |
1991 |
| Předmět: |
|
| Zdroj: |
Journal of molecular biology. 218(4) |
| ISSN: |
0022-2836 |
| Popis: |
To clarify the functional role of Tyr-42(C7) alpha, which forms a hydrogen bond with Asp-99(G1) beta at the alpha 1-beta 2 interface of human deoxyhaemoglobin, we engineered two artificial mutant haemoglobins (Hb), in which Tyr-42 alpha was replaced by Phe (Hb Phe-42 alpha) or His (Hb His-42 alpha), and investigated their oxygen binding properties together with structural consequences of the mutations by using various spectroscopic probes. Like most of the natural Asp-99 beta mutants, Hb Phe-42 alpha showed a markedly increased oxygen affinity, a reduced Bohr effect and diminished co-operativity. Structural probes such as ultraviolet-region derivative and oxy-minus-deoxy difference spectra, resonance Raman scattering and proton nuclear magnetic resonance spectra indicate that, in Hb Phe-42 alpha, the deoxy T quaternary structure is highly destabilized and the strain imposed on the Fe-N epsilon (proximal His) bond is released, stabilizing the oxy tertiary structure. In contrast with Hb Phe-42 alpha, Hb His-42 alpha showed an intermediately impaired function and only moderate destabilization of the T-state, which can be explained by the formation of a new, weak hydrogen bond between His-42 alpha and Asp-99 beta. Spectroscopic data were consistent with this assumption. The present study proves that the hydrogen bond between Tyr-42 alpha and Asp-99 beta plays a key role in stabilizing the deoxy T structure and consequently in co-operative oxygen binding. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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