1H NMR spectroscopic studies of calcium-binding proteins. 2. Histidine microenvironments in alpha- and beta-parvalbumins as determined by protonation and laser photochemically induced dynamic nuclear polarization effects.
1H NMR spectroscopic studies of calcium-binding proteins. 2. Histidine microenvironments in alpha- and beta-parvalbumins as determined by protonation and laser photochemically induced dynamic nuclear polarization effects.
复制标题
钙结合蛋白的 1H NMR 光谱研究。
作者：
T. C. Williams;D. Corson;W. Mccubbin;K. Oikawa;C. Kay;B. Sykes
用1H NMR技术研究了三种Ca（II）结合的小白蛋白（鲤鱼，pI = 4.25; pike, pI = 5.00；大鼠，pI = 5.50）中组氨酸的微环境，以探讨它们的质子化特性和光化学诱导的动态核极化（photocidnp）。26位（或25位）的组氨酸存在于这三种蛋白质中，其C2H或C5H共振完全没有光- cidnp增强。这种非极化组氨酸也不具有正常的pKa：其值仅从鲤鱼的4.20到梭鱼的4.32到大鼠的4.44不等。随着pH值的降低，该鲤鱼异构体组氨酸的C2H和C5H共振分裂成双峰。这种分裂的程度取决于磁场强度、温度和pH值；然而，每个重态内的谱线强度与温度无关。尽管鲤鱼小白蛋白的晶体结构表明His-26暴露于溶剂中[Kretsinger， R. H., & Nockolds， C. E.(1973)]。化学，248,3313-3326]，我们得出结论，在溶液中，该残基处于非质子化状态，是蛋白质疏水核心的一部分。相比之下，大鼠小白蛋白中的His-48和pike III小白蛋白中的His-106显示出其C2H， C5H和β - ch21h核磁共振的光- cidnp增强。结合其接近正常的pKa、6.14和交换加宽的C2H共振，His-48的光- cidnp增强结果表明，它的微环境与随机线圈暴露的微环境差别不大，与它在螺旋c的溶剂表面的假定位置一致。
The microenvironments of the histidines in three isoforms of Ca(II)-bound parvalbumin (carp, pI = 4.25; pike, pI = 5.00; rat, pI = 5.50) have been examined with 1H NMR techniques to probe their protonation characteristics and photochemically induced dynamic nuclear polarizability (photo-CIDNP). The histidine at position 26 (or 25), present in all three of these proteins, shows absolutely no photo-CIDNP enhancement of its C2H or C5H resonances. Nor does this nonpolarizable histidine possess a normal pKa: values range only from 4.20 for carp to 4.32 for pike to 4.44 for rat. The C2H and C5H resonances of the histidine in this carp isoform split into doublets as the pH is lowered. The magnitude of this splitting depends on the magnetic field strength, temperature, and pH; however, the line intensities within each doublet are temperature-independent. Although the crystal structure of carp parvalbumin indicates that His-26 is exposed to solvent [Kretsinger, R. H., & Nockolds, C. E. (1973) J. Biol. Chem. 248, 3313-3326], we conclude that in solution this residue, in its unprotonated state, is part of the hydrophobic core of the protein. In contrast, His-48 in rat parvalbumin and His-106 in pike III parvalbumin show dramatic photo-CIDNP enhancements of their C2H, C5H, and beta-CH2 1H NMR resonances. Combined with its nearly normal pKa, 6.14, and exchange-broadened C2H resonance, the photo-CIDNP enhancement results for His-48 indicate that its microenvironment differs little from random-coil exposure, consistent with its presumed position on the solvent surface of helix C.(ABSTRACT TRUNCATED AT 250 WORDS)
肌红蛋白血红素腔中滴定基团的识别。
DOI：
10.1111/j.1432-1033.1984.tb07892.x
发表时间：
1984
期刊：
European journal of biochemistry
影响因子：
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作者：
Krishnamoorthi,R;LaMar,GN
通讯作者：
LaMar,GN