Ragone R, Colonna G, Bismuto E, Irace G
Biochemistry. 1987 Apr 21;26(8):2130-4. doi: 10.1021/bi00382a010.
The effects of denaturants on the solvent accessibility to tyrosyl residues of apomyoglobin have been examined by means of second-derivative spectroscopy in the near-ultraviolet. Three apomyoglobins, i.e., sperm whale, horse, and tuna, were selected because of the different distribution of tyrosyl residues in their primary structure. The results are consistent with the occurrence of two independent consecutive events in the guanidine-induced denaturation pattern of apomyoglobin. The first event, which is responsible for the lack of the ability to bind the heme, has been proved to involve conformational changes in both the domains, i.e., segments 1-79 and 80-153, identified in the myoglobin molecule. However, the conformational changes are not of the same type. In fact, the solvent accessibility to tyrosine HC2 is increased probably because of a partial unfolding of the 80-153 domain. Conversely, the solvent accessibility to tyrosine B2 is decreased, thus indicating that a refolding occurs in some region of the N-terminal moiety (1-79 domain) of the molecule.
已通过近紫外区的二阶导数光谱法研究了变性剂对脱辅基肌红蛋白酪氨酸残基溶剂可及性的影响。选择了三种脱辅基肌红蛋白，即抹香鲸、马和金枪鱼的脱辅基肌红蛋白，因为它们一级结构中酪氨酸残基的分布不同。结果与脱辅基肌红蛋白胍诱导变性模式中两个独立的连续事件的发生一致。第一个事件导致无法结合血红素，已证明该事件涉及肌红蛋白分子中确定的两个结构域（即1-79段和80-153段）的构象变化。然而，构象变化并非同一类型。事实上，酪氨酸HC2的溶剂可及性增加，可能是由于80-153结构域部分展开。相反，酪氨酸B2的溶剂可及性降低，这表明分子N端部分（1-79结构域）的某些区域发生了重折叠。
