Tomita Ayana, Sato Tokushi, Nozawa Shunsuke, Koshihara Shin-ya, Adachi Shin-ichi
Department of Materials Science, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan.
Acta Crystallogr A. 2010 Mar;66(Pt 2):220-8. doi: 10.1107/S0108767309050752. Epub 2010 Feb 9.
In order to explore the ligand-migration dynamics in myoglobin induced by photodissociation, cryogenic X-ray crystallographic investigations of carbonmonoxy myoglobin crystals illuminated by continuous wave and pulsed lasers at 1-15 kHz repetition rate have been carried out. Here it is shown that this novel method, extended pulsed-laser pumping of carbonmonoxy myoglobin, promotes ligand migration in the protein matrix by crossing the glass transition temperature repeatedly, and enables the visualization of the migration pathway of the photodissociated ligands in native Mb at cryogenic temperatures. It has revealed that the migration of the CO molecule into each cavity induces structural changes of the amino-acid residues around the cavity which result in the expansion of the cavity. The sequential motion of the ligand and the cavity suggests a self-opening mechanism of the ligand-migration channel arising by induced fit.
为了探索光解离诱导的肌红蛋白中配体迁移动力学，我们对一氧化碳肌红蛋白晶体进行了低温X射线晶体学研究，该晶体由连续波和脉冲激光以1 - 15 kHz的重复频率照射。结果表明，这种新型方法，即对一氧化碳肌红蛋白进行扩展脉冲激光泵浦，通过反复跨越玻璃化转变温度促进了蛋白质基质中的配体迁移，并能够在低温下可视化天然肌红蛋白中光解离配体的迁移途径。研究发现，CO分子迁移到每个腔中会引起腔周围氨基酸残基的结构变化，从而导致腔的扩张。配体和腔的顺序运动表明了由诱导契合产生的配体迁移通道的自开放机制。
