CHARACTERIZATION OF MULTIPLE BENDS IN PROTEINS
CHARACTERIZATION OF MULTIPLE BENDS IN PROTEINS
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DOI：
10.1002/bip.1980.360190607
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发表时间：
1980-01-01
期刊：
影响因子：
2.9
通讯作者：
SCHERAGA, HA
中科院分区：
文献类型：
--
作者：
ISOGAI, Y;NEMETHY, G;SCHERAGA, HA
折弯或链反转的概念[非螺旋二肽序列，其中Cα之间的距离R3(i，i+3)。残基I和I+3的原子为。7.0.ANG.]将双弯定义为三肽序列，而不是在α-螺旋中，其中2个连续距离R3(i，i+3)和R3(i+1，i+4)是α-螺旋。7.0.，具有对更高阶多折弯的类似定义。一个由4050个残基组成的23个蛋白质样本，包含235个单弯、58个双弯和11个高阶多弯。作为标准的I型、II型和III型链反转(以及它们的镜像)的组合，可能会发生多个弯曲，但通常它们需要从这些明确定义的构象中扭曲。氨基酸的出现频率在单弯和多弯之间往往有很大的不同。R3距离的概率分布在单弯和多弯中没有不同。R4(C.Alpha之间的距离。残基I和I+4的原子)在多个弯曲中通常比在包含单弯曲的三肽序列中短。在许多多个弯曲中，R4的值接近于α-螺旋的值。在其他一些多弯中，R4甚至更短，表明这些结构非常紧凑。关于连接Cα的虚键的二面角的符号。原子以及通过微分几何定义的曲率和挠率的值表明，单弯和多弯倾向于右手(例如，像α-螺旋序列)，并且在许多多弯的单弯部件中有强烈的保持惯用手的倾向。这些通常与α-螺旋的扭曲单圈有很大的相似之处，并且不构成链反转。双弯曲，其中两个连续的虚键二面角的符号不同，具有与α螺旋非常不同的构象。它们的作用是发生在3个残基上的链逆转。这些链条反转以前没有描述过。多个弯曲可能在蛋白质折叠中发挥重要作用，因为它们相当频繁地出现在蛋白质中，并导致多肽链方向的重大变化。
The concept of bends or chain reversals [nonhelical dipeptide sequences in which the distance R3 (i, i + 3) between the C.alpha. atoms of residues i and i + 3 is .ltoreq. 7.0 .ANG.] was extended to define double bends as tripeptide sequences, not in an .alpha.-helix, in which 2 successive distances R3(i, i + 3) and R3 (i + 1, i + 4) are .ltoreq. 7.0 .ANG., with analogous definitions for higher-order multiple bends. A sample of 23 proteins, consisting of 4050 residues, contains 235 single, 58 double and 11 higher-order multiple bends. Multiple bends may occur as combinations of the standard type I, II and III chain reversals (as well as their mirror images), but usually they require distortions from these well-defined conformations. The frequency of occurrence of amino acids often differs significantly between single and multiple bends. The probability distribution of R3 distances does not differ in single and multiple bends. R4 (the distance between the C.alpha. atoms of residues i and i + 4) in multiple bends is generally shorter than in tripeptide sequences containing single bends. The value of R4 in many multiple bends is near those for .alpha.-helices. In some other multiple bends, R4 is even shorter, indicating that these structures are very compact. The signs of the dihedral angles about the virtual bonds connecting C.alpha. atoms and the values of curvature and torsion, as defined by means of differential geometry, indicate that there is a preference for single and multiple bends to be right-handed (like an .alpha.-helical sequence, for example) and that there is a strong tendency to conserve the handedness in single-bend components of many multiple bends. These often have a strong resemblance to distorted single turns of an .alpha.-helix and do not constitute chain reversals. Double bends, in which the signs of 2 successive virtual-bond dihedral angles differ, have conformations that are very different from an .alpha.-helix. They act as chain reversals occurring over 3 residues. These chain reversals were not previously described. Multiple bends may play an important role in protein folding because they occur fairly frequently in proteins and cause major changes in the direction of the polypeptide chain.