Structure Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark.
Biochemistry. 2010 Apr 20;49(15):3246-53. doi: 10.1021/bi902125j.
Secondary chemical shift analysis has been used to characterize the unfolded state of acid-denatured c-src SH3. Even though native c-src SH3 adopts an all-beta fold, we found evidence of transient helicity in regions corresponding to native loops. In particular, residues 40-46, connecting the n-src loop to the third beta-strand, exhibited an apparent helicity of nearly 45%. Furthermore, the RT loop and the diverging turn appeared to adopt non-native-like helical conformations. Interestingly, none of the residues found in transient helical conformations exhibited significant varphi-values [Riddle, D. S., et al. (1999) Nat. Struct. Biol. 6, 1016-1024]. This indicated that the transient helicity has no influence or only a weak influence on the actual protein folding reaction. The residual structural propensities were compared to those of other SH3 domains, revealing heterogeneity in the unfolded ensemble that clearly contrasts with the conserved character of the topology of native state and transition state ensembles typical for SH3 domains.
二级化学位移分析已被用于表征酸变性 c-src SH3 的无规则状态。尽管天然 c-src SH3 采用全β折叠结构，但我们发现了在对应于天然环的区域中存在瞬态螺旋的证据。特别是，连接 n-src 环和第三个β-链的残基 40-46 表现出近 45%的明显螺旋性。此外，RT 环和发散转角似乎采用了非天然样的螺旋构象。有趣的是，在瞬态螺旋构象中发现的任何残基都没有表现出显著的 varphi 值[Riddle, D. S., et al. (1999) Nat. Struct. Biol. 6, 1016-1024]。这表明瞬态螺旋对实际蛋白质折叠反应没有影响或只有微弱的影响。剩余的结构倾向与其他 SH3 结构域进行了比较，揭示了无规卷曲集合体中的异质性，这与 SH3 结构域典型的天然状态和过渡态集合体拓扑结构的保守特征形成了鲜明对比。
