在纳秒时间域内一氧化碳重新结合时产生最大双分子产率的肌红蛋白突变体。
Myoglobin mutants giving the largest geminate yield in CO rebinding in the nanosecond time domain.
作者信息
Sugimoto T, Unno M, Shiro Y, Dou Y, Ikeda-Saito M
机构信息
Faculty of Science, Gakushuin University, Mejiro, Toshima-ku, Tokyo 170, Japan.
出版信息
Biophys J. 1998 Nov;75(5):2188-94. doi: 10.1016/S0006-3495(98)77662-3.
We have measured the rebinding of carbon monoxide (CO) to some distal mutants of myoglobin (Mb) in the time range from 10(-8) to 10(-1) s by flash photolysis, in which the photodissociated CO rebinds to the heme iron without escaping to the solvent water from the protein matrix. We have found that the double mutants [His64-->Val/Val68-->Thr (H64V/V68T) and His64-->Val/Val68-->Ser (H64V/V68S)] have an extremely large geminate yield (70-80%) in water at 5 degreesC, in contrast to the 7% of the geminate yield of wild-type Mb. The CO geminate yields for these two mutants are the largest in those of Mb mutants reported so far, showing that the two mutants have a unique heme environment that favors CO geminate rebinding. Comparing the crystal structures and 1H-NMR and vibrational spectral data of H64V/V68T and H64V/V68S with those of other mutants, we discuss factors that may control the nanosecond geminate CO rebinding and CO migration in the protein matrix.
我们通过闪光光解在10⁻⁸至10⁻¹秒的时间范围内测量了一氧化碳（CO）与肌红蛋白（Mb）一些远端突变体的再结合情况，其中光解离的CO重新结合到血红素铁上，而不会从蛋白质基质逃逸到溶剂水中。我们发现，双突变体[His64→Val/Val68→Thr（H64V/V68T）和His64→Val/Val68→Ser（H64V/V68S）]在5℃的水中具有极高的双分子产率（70 - 80%），相比之下，野生型Mb的双分子产率为7%。这两个突变体的CO双分子产率在迄今报道的Mb突变体中是最高的，表明这两个突变体具有有利于CO双分子再结合的独特血红素环境。通过比较H64V/V68T和H64V/V68S与其他突变体的晶体结构、¹H - NMR和振动光谱数据，我们讨论了可能控制蛋白质基质中纳秒级双分子CO再结合和CO迁移的因素。
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