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首页> 外文期刊>Journal of Molecular Biology >NMR Investigation of the Dynamics of Tryptophan Side-chains in Hemoglobins.
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NMR Investigation of the Dynamics of Tryptophan Side-chains in Hemoglobins.

机译：血红蛋白中色氨酸侧链动力学的NMR研究。

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NMR relaxation measurements of 15N spin-lattice relaxation rate (R(1)), spin-spin relaxation rate (R(2)), and heteronuclear nuclear Overhauser effect (NOE) have been carried out at 11.7T and 14.1T as a function of temperature for the side-chains of the tryptophan residues of 15N-labeled and/or (2H,15N)-labeled recombinant human normal adult hemoglobin (Hb A) and three recombinant mutant hemoglobins, rHb Kempsey (betaD99N), rHb (alphaY42D/betaD99N), and rHb (alphaV96W), in the carbonmonoxy and the deoxy forms as well as in the presence and in the absence of an allosteric effector, inositol hexaphosphate (IHP). There are three Trp residues (alpha14, beta15, and beta37) in Hb A for each alphabeta dimer. These Trp residues are located in important regions of the Hb molecule, i.e. alpha14Trp and beta15Trp are located in the alpha(1)beta(1) subunit interface and beta37Trp is located in the alpha(1)beta(2) subunit interface. The relaxation experiments show that amino acid substitutions in the alpha(1)beta(2) subunit interface can alter the dynamics of beta37Trp. The transverse relaxation rate (R(2)) for beta37Trp can serve as a marker for the dynamics of the alpha(1)beta(2) subunit interface. The relaxation parameters of deoxy-rHb Kemspey (betaD99N), which is a naturally occurring abnormal human hemoglobin with high oxygen affinity and very low cooperativity, are quite different from those of deoxy-Hb A, even in the presence of IHP. The relaxation parameters for rHb (alphaY42D/betaD99N), which is a compensatory mutant of rHb Kempsey, are more similar to those of Hb A. In addition, TROSY-CPMG experiments have been used to investigate conformational exchange in the Trp residues of Hb A and the three mutant rHbs. Experimental results indicate that the side-chain of beta37Trp is involved in a relatively slow conformational exchange on the micro- to millisecond time-scale under certain experimental conditions. The present results provide new dynamic insights into the structure-function relationship in hemoglobin.
机译：作为函数，对15N自旋晶格弛豫率（R（1）），自旋自旋弛豫率（R（2））和异核核Overhauser效应（NOE）进行NMR弛豫测量15N标记和/或（2H，15N）标记的重组人正常成人血红蛋白（Hb A）和三种重组突变体血红蛋白rHb Kempsey（betaD99N），rHb（alphaY42D / βD99N）和rHb（alphaV96W）形式的一氧化碳和脱氧形式，以及在存在和不存在变构效应物肌醇六磷酸（IHP）的情况下。每个字母二聚体在Hb A中存在三个Trp残基（alpha14，beta15和beta37）。这些Trp残基位于Hb分子的重要区域，即alpha14Trp和beta15Trp位于alpha（1）beta（1）亚基界面中，而beta37Trp位于alpha（1）beta（2）亚基界面中。弛豫实验表明，alpha（1）beta（2）亚基界面中的氨基酸取代可以改变beta37Trp的动力学。 beta37Trp的横向弛豫率（R（2））可以用作alpha（1）beta（2）亚基界面动力学的标记。脱氧-rHb Kemspey（betaD99N）的松弛参数是天然存在的异常人类血红蛋白，具有高的氧亲和力和非常低的协同性，即使在存在IHP的情况下，其松弛参数也与脱氧-Hb A完全不同。作为rHb Kempsey的补偿性突变体的rHb（alphaY42D / betaD99N）的弛豫参数与Hb A的弛豫参数更相似。此外，TROSY-CPMG实验已用于研究Hb A的Trp残基中的构象交换。和三个突变体rHbs。实验结果表明，在某些实验条件下，beta37Trp的侧链在微秒至毫秒的时间尺度上参与相对缓慢的构象交换。目前的结果为血红蛋白中的结构-功能关系提供了新的动态见解。

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