Structure and evolution of parallel β-helix proteins
Structure and evolution of parallel β-helix proteins
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DOI：
10.1006/jsbi.1998.3985
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发表时间：
1998-01-01
影响因子：
3
通讯作者：
Pickersgill, R
中科院分区：
文献类型：
--
作者：
Jenkins, J;Mayans, O;Pickersgill, R
三种细菌果胶裂解酶，一种来自黑曲霉的果胶裂解酶，一种来自刺曲霉的鼠李糖半乳糖醛酸酶a， RGase a和p22噬菌体尾穗蛋白，TSP的结构显示出在果胶裂解酶中首次发现的右旋平行β -螺旋结构。裂解酶有7个完整的线圈，而RGase A和TSP分别有11个和12个完整的线圈。每个线圈包含三个β -链和三个旋转区域，依次命名为PB1， T1, PB2, T2， PB3和T3。裂解酶具有同源序列，但RGase A和TSP与裂解酶之间或彼此之间都没有明显的序列同源性。然而，所有这些分子之间的结构相似性是如此广泛，以至于从一个共同祖先分化的可能性比收敛到同一褶皱的可能性要大得多。PB2-T2-PB3区是裂解酶中最保守的区域，显示出最强烈的结构相似性。然而，它们的整体形状、长环的位置、覆盖平行β -螺旋的氨基末端的保守α -螺旋以及PB1起始α (R)-构象的堆积都表明它们有共同的祖先，功能上的相似性。这些酶都在包含PB1及其两个侧翼旋转区域的等效位点结合含有α -半乳糖的聚合物，这进一步支持了分化进化。我们认为，线圈的堆叠和PB2和PB3不寻常的接近垂直的连接使得平行的β -螺旋折叠在分化进化过程中尤其可能保持相似的主链构象，即使在初级结构的所有相似性痕迹消失之后(C) 1998学术出版社。
Three bacterial pectate lyases, a pectin lyase from Aspergillus niger, the structures of rhamnogalacturonase A from Aspergillus aculeatus, RGase A, and the P22-phage tailspike protein, TSP, display the right-handed parallel beta-helix architecture first seen in pectate lyase. The lyases have 7 complete coils while RGase A and TSP have 11 and 12, respectively. Each coil contains three beta-strands and three turn regions named PB1, T1, PB2, T2, PB3, and T3 in their order of occurrence. The lyases have homologous sequences but RGase A and TSP do not show obvious sequence homology either to the lyases or to each other. However the structural similarities between all these molecules are so extensive that divergence from a common ancestor is much more probable than convergence to the same fold, The region PB2-T2-PB3 is the best conserved region in the lyases and shows the dearest structural similarity. Not only is the pleating and the direction of the hydrogen bonding in the sheets conserved, but so is the unusual alpha(L)-conformation turn between the two sheets, However, the overall shape, the position of long loops, a conserved alpha-helix that covers the amino-terminal end of the parallel beta-helix and stacks of residues in alpha(R)-conformation at the start of PB1 all suggest a common ancestor, The functional similarity, that the enzymes all bind alpha-galactose containing polymers at an equivalent site involving PB1 and its two flanking turn regions, further supports divergent evolution. We suggest that the stacking of the coils and the unusual near perpendicular junction of PB2 and PB3 make the parallel beta-helix fold especially likely to maintain similar main chain conformations during divergent evolution even after all vestige of similarity in primary structure has vanished (C) 1998 Academic Press.