DYNAMIC PROTEIN STRUCTURES - INFRARED EVIDENCE FOR 4 DISCRETE RAPIDLY INTERCONVERTING CONFORMERS AT THE CARBON-MONOXIDE BINDING-SITE OF BOVINE HEART MYOGLOBIN
DYNAMIC PROTEIN STRUCTURES - INFRARED EVIDENCE FOR 4 DISCRETE RAPIDLY INTERCONVERTING CONFORMERS AT THE CARBON-MONOXIDE BINDING-SITE OF BOVINE HEART MYOGLOBIN
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DOI：
10.1073/pnas.78.5.2903
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发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
TUCKER, MP
中科院分区：
文献类型：
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作者：
CAUGHEY, WS;SHIMADA, H;TUCKER, MP
随着 pH 或温度的变化，在 C-O 拉伸区域仔细检查了 CM 复合物与肌红蛋白 [Mb] 的红外光谱，肌红蛋白 [Mb] 是从牛心肌中分离出来的氧酰基物质。将这些光谱解卷积成高斯形状的带表明在 1938(I)、1944(II)、1954(III) 和 1965(IV) cm-1 附近存在 4 个带，半带宽度分别约为 18、9、9 和 10 cm-1。 4 个条带的相对强度随着 pH 值或温度的变化而变化。 13C NMR 谱和其他证据表明 4 C.sbd.O 拉伸带源自 4 个离散的快速互变构象异构体：CI、CII、CIII 和 CIV。在生理pH和温度条件下，相对稳定性为CI.apprxeq。 CII .mchgt。 CIII.apprxeq。 CIV。构象异构体互变的ΔH和ΔS值估计范围分别为-8至34 kJ/mol和-27至87 J.cntdot.mol-1 K-1；构象异构体的结构可能有很大差异。这些发现为牛肌红蛋白的配体结合位点具有高度灵活的动态结构提供了证据，即使配体已结合。
IR spectra for the CM complex with myoglobin [Mb] isolated as the oxygenyl species from bovine heart muscle were carefully examined in the C-O stretch region as either the pH or the temperature was varied. Deconvolutions of these spectra into bands of Gaussian shape suggest the presence of 4 bands near 1938(I), 1944(II), 1954(III) and 1965(IV) cm-1 with halfband widths of about 18, 9, 9 and 10 cm-1, respectively. The relative intensities of the 4 bands varied with changes in pH or temperature. 13C NMR spectra and other evidence indicate that the 4 C.sbd.O stretch bands arise from 4 discrete rapidly interconverting conformers: CI, CII, CIII and CIV. Under conditions of physiological pH and temperature, the relative stabilities are CI .apprxeq. CII .mchgt. CIII .apprxeq. CIV. The .DELTA.H and .DELTA.S values for conformer interconversions are estimated to range from -8 to 34 kJ/mol and -27 to 87 J.cntdot.mol-1 K-1, respectively; the structures of the conformers may vary significantly. These findings provide evidence for a highly flexible, dynamic structure at the ligand-binding site of bovine myoglobin, even when ligands are bound.