Stereochemical restrictions on the occurrence of amino acid residues in the collagen structure.
Stereochemical restrictions on the occurrence of amino acid residues in the collagen structure.
复制标题
立体化学限制胶原蛋白结构中氨基酸残基的出现。
DOI：
10.1111/j.1399-3011.1977.tb03485.x
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
M. Bansal
中科院分区：
文献类型：
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作者：
M. Bansal
胶原蛋白的一级结构由重复的三肽序列（Gly-R2-R3）n表征。理论研究的结果，进行接触标准来计算的立体化学允许的各种侧链在位置2和3的取向，在这里报告。发现仅具有γ-原子的侧链，如在缬氨酸、丝氨酸和苏氨酸中，或仅具有一个δ-甲基的侧链，如在异亮氨酸中，可以同样好地出现在位置2和3处，如在胶原中的实际情况。具有两个C δ原子的侧链，如亮氨酸和苯丙氨酸，也可以容纳在两个位置。然而，如果它们作为R3存在，则在相邻链中存在作为R2的脯氨酸残基的情况下，它们的取向自由度受到严重限制。如果假定存在与三螺旋链结合的水分子，则位置3几乎不可能存在亮氨酸和苯丙氨酸残基。然而，位置2不受影响，并且它们作为R2的存在可以帮助保护水分子免受溶剂介质的干扰。这可能是Leu和Phe残基优先出现在胶原三联体中位置2的原因，尽管多肽（Gly-Pro-Leu）n和（Gly-Pro-Phe）n形成胶原样结构。
The primary structure of collagen is characterized by the repeating tripeptide sequence (Gly-R2-R3)n. The results of theoretical studies, carried out using contact criteria to compute the stereochemically allowed orientations for various side chains at locations 2 and 3, are reported here. It is found that side chains with only gamma-atoms, as in valine, serine and threonine, or with only one delta-methyl group, as in isoleucine, can occur equally well at locations 2 and 3, as is actually the case in collagen. Side chains with two Cdelta-atoms, as in leucine and phenylalanine, can also be accommodated at both positions. However, if they occur as R3, their freedom of orientation is severely restricted in the presence of a proline residue as R2 in a neighbouring chain. If water molecules bound to the chains of the triple helix are assumed to be present, then location 3 is virtually impossible for leucine and phenylalanine residues. Location 2 is, however, unaffected, and their presence as R2 can help to shield the water molecules from disturbance by the solvent medium. This may be the reason for the preferential occurrence of Leu and Phe residues in location 2 in the collagen triplets, although the polypeptides (Gly-Pro-Leu)n and (Gly-Pro-Phe)n form collagen-like structures.