Matthews S J, Jandu S K, Leatherbarrow R J
Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London, U.K.
Biochemistry. 1993 Jan 19;32(2):657-62. doi: 10.1021/bi00053a034.
Recombinant chymotrypsin inhibitor 2 (CI-2) and the three mutants Ile39-->Val, Ile39-->Leu, and Arg67-->Ala were successfully enriched with [2-13C]tryptophan at position 24 within the hydrophobic core of the protein. Carbon-13 NMR relaxation measurements were then used to investigate the effect of these mutations on the dynamics of the tryptophan residue. In addition, the stability of wild-type and mutant CI-2s was measured by their susceptibility to unfolding by guanidine hydrochloride. The mutant proteins were all found to be less stable, giving delta delta GU values relative to wild-type of 1.17, 1.96, and 1.21 kcal mol-1, respectively. The indole moiety of the tryptophan residue was found to be more mobile in all the mutants studied than in wild-type CI-2. Order parameters of 0.69, 0.60, 0.56, and 0.44 were derived for wild-type, Ile39-->Val, Ile39-->Leu, and Arg67-->Ala CI-2, respectively. It is concluded that there is a correlation between the protein stability and the picosecond dynamics within the hydrophobic core and that mutations can influence the dynamic behavior of the residues that are relatively distant in the three-dimensional structure.
重组胰凝乳蛋白酶抑制剂2（CI-2）及其三个突变体Ile39→Val、Ile39→Leu和Arg67→Ala在蛋白质疏水核心区的第24位成功地用[2-¹³C]色氨酸进行了富集。然后利用碳-13核磁共振弛豫测量来研究这些突变对色氨酸残基动力学的影响。此外，通过野生型和突变型CI-2对盐酸胍展开的敏感性来测量它们的稳定性。发现所有突变蛋白的稳定性都较低，相对于野生型的ΔΔGU值分别为1.17、1.96和1.21 kcal mol⁻¹。发现在所有研究的突变体中，色氨酸残基的吲哚部分比野生型CI-2中的更具流动性。野生型、Ile39→Val、Ile39→Leu和Arg67→Ala CI-2的序参数分别为0.69、0.60、0.56和0.44。得出的结论是，蛋白质稳定性与疏水核心区内的皮秒动力学之间存在相关性，并且突变可影响三维结构中相对较远残基的动态行为。
