High pressure NMR studies of hemoproteins. The effect of pressure on the quaternary structure of hemoglobin |
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Authors: | Isao Morishima Mitsunobu Hara |
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Institution: | Division of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 606, Japan |
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Abstract: | Proton NMR spectra for nitrosyl-, aquomet- and deoxy des-Arg(α141)-hemoglobin in H2O were studied at high pressures up to 1400 atm with attention to the exchangeable proton resonances due to the intra- and intersubunit hydrogen bonds. For aquomethemoglboin, the T state marker signal at 6.4 ppm is insensitive to pressure while the R state marker signal at 6.0 ppm exhibits progressive upfield shift upon pressurization. For nitrosylhemoglobin, the T state signals at 9.6 and 6.5 ppm decrease their intensities upon pressurization while the R state marker signal at 6.0ppm remains unchanged. Pressure-induced spectral changes for some of exchangeable resonances are also encountered for deoxy des-Arg(α141)-hemoglobin while the R and T quaternary structural indicators at 6.0 and 9.4 ppm are insensitive to pressure. These pressure-induced spectral changes for these hemoglobin derivatives are significantly distinguished from those associated with the R-T transition induced by addition of IHP or by variatiuon of pH. It is therefore concluded that pressure induces subtle quaternary structural changes in these hemoglobin derivatives without causing the R-T transition. |
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Keywords: | POMC pro-opiomelanocortin ACTH adrenocorticotropin β-LPH β-lipotropin 16K fragment 16 000 Dalton fragment of POMC γ-MSH γ-melanotropin RP-HPLC reversed-phase high performance liquid chromatography ODS-silica octadecylsilyl-silica TFA trifluoroacetic acid |
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