A rare polyglycine type II‐like helix motif in naturally occurring proteins
A rare polyglycine type II‐like helix motif in naturally occurring proteins
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DOI：
10.1002/prot.25355
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发表时间：
2017-11
期刊：
影响因子：
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通讯作者：
E. Warkentin;S. Weidenweber;Karola Schühle;U. Demmer;J. Heider;U. Ermler
中科院分区：
文献类型：
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作者：
E. Warkentin;S. Weidenweber;Karola Schühle;U. Demmer;J. Heider;U. Ermler
蛋白质中常见的结构元素，如α -螺旋或β -片，其特征是均匀重复的，能量有利的主链构象，另外还表现出主链NH和CO基团的完全饱和的氢键网络。虽然在蛋白质中经常发现聚脯氨酸或聚甘氨酸II型螺旋（PPII或PGII），但它们不被认为是等效的二级结构元素，因为它们不形成类似的主链原子的自含氢键网络。在这种情况下，我们在苯乙酮羧化酶核心复合物的结构中发现了一个不寻常的富含甘氨酸的PGII样螺旋基序，这是相关的。这些类PGII螺旋形成六角形束，似乎满足主链基团（很大程度上）饱和氢键网络的标准，因此可以从这个意义上看作是一个新的二级结构元素。它由一个中心的PGII - like螺旋组成，周围环绕着六个几乎平行的PGII - like螺旋，形成一个六边形阵列，另外还有一个向外延伸的PGII - like螺旋。以前在合成聚甘氨酸纤维中发现了非常相关的结构元素。在这两种情况下，PGII -螺旋中心的所有主链nhh和CO基团都被分子内或分子间氢键饱和，从而形成一个自包含的氢键网络。在GTP结合蛋白和抗冻蛋白中也发现了类似但不完整的PGII -螺旋模式。
Common structural elements in proteins such as α‐helices or β‐sheets are characterized by uniformly repeating, energetically favorable main chain conformations which additionally exhibit a completely saturated hydrogen‐bonding network of the main chain NH and CO groups. Although polyproline or polyglycine type II helices (PPII or PGII) are frequently found in proteins, they are not considered as equivalent secondary structure elements because they do not form a similar self‐contained hydrogen‐bonding network of the main chain atoms. In this context our finding of an unusual motif of glycine‐rich PGII‐like helices in the structure of the acetophenone carboxylase core complex is of relevance. These PGII‐like helices form hexagonal bundles which appear to fulfill the criterion of a (largely) saturated hydrogen‐bonding network of the main‐chain groups and therefore may be regarded in this sense as a new secondary structure element. It consists of a central PGII‐like helix surrounded by six nearly parallel PGII‐like helices in a hexagonal array, plus an additional PGII‐like helix extending the array outwards. Very related structural elements have previously been found in synthetic polyglycine fibers. In both cases, all main chain NH and CO groups of the central PGII‐helix are saturated by either intra‐ or intermolecular hydrogen‐bonds, resulting in a self‐contained hydrogen‐bonding network. Similar, but incomplete PGII‐helix patterns were also previously identified in a GTP‐binding protein and an antifreeze protein.