CONFORMATION OF AMINO-ACID SIDE-CHAINS IN PROTEINS
CONFORMATION OF AMINO-ACID SIDE-CHAINS IN PROTEINS
复制标题
DOI：
10.1016/0022-2836(78)90408-4
复制
发表时间：
1978-01-01
影响因子：
5.6
通讯作者：
MAIGRET, B
中科院分区：
文献类型：
--
作者：
JANIN, J;WODAK, S;MAIGRET, B
分析了19种蛋白质结构的2536个残基的侧链二面角。将χ 1和χ 2的分布与基于简单能量计算所作的预测进行比较。χ 1分布是三峰的;侧链的g-位（反式至H α），除了在丝氨酸、T位（氨基的反式）和G+位（羰基的反式）中是罕见的，G+位在所有残基中是优选的。对于具有四面体γ-的残基观察到特征χ 2分布。碳，芳族残基和天冬氨酸/天冬酰胺。对于所有类型的侧链，实际观察到的构型数量都很小，其中60%或更多的侧链只有1或2种构型。在χ 1和χ 2上的实验误差的估计（3 °- 16 °，取决于残基的类型）;二面角保持在15 °以内。18.degree.（标准偏差）与具有最低计算能量的构型的差。允许的配置之间的侧链的分布略有不同的构象的主链，并与相对于蛋白质表面的残基的位置。暴露的残基是罕见的，甚至更罕见的掩埋的残基，这表明，虽然折叠的结构把侧链构象的应变很小，侧链的位置，在未折叠的结构中具有最低的能量被优先选择在折叠。
The side-chain dihedral angles were analyzed in 2536 residues from 19 protein structures. The distributions of .chi.1 and .chi.2 were compared with predictions made on the basis of simple energy calculations. The .chi.1 distribution is trimodal; the g- position of the side-chain (trans to H.alpha.), which is rare except in serine, the t position (trans to the amino group), and the g+ position (trans to the carbonyl group), which is preferred in all residues. Characteristic .chi.2 distributions are observed for residues with a tetrahedral .gamma.-carbon, for aromatic residues, and for aspartic acid/asparagine. The number of configurations actually observed is small for all types of side-chains, with 60% or more of them in only 1 or 2 configurations. Estimates of the experimental errors on .chi.1 and .chi.2 (3.degree.-16.degree., depending on the type of the residue) are given; the dihedral angles remain within 15.degree.-18.degree. (standard deviation) from the configurations with the lowest calculated energies. The distribution of the side-chains among the permitted configurations varies slightly with the conformation of the main chain, and with the position of the residue relative to the protein surface. Configurations that are rare for exposed residues are even rarer for buried residues, suggesting that, while the folded structure puts little strain on side-chain conformations, the side-chain positions with the lowest energy in the unfolded structure are chosen preferentially during folding.