Wuilmart C, Urbain J
Eur J Biochem. 1984 Feb 15;139(1):35-40. doi: 10.1111/j.1432-1033.1984.tb07972.x.
Weak but recurrent periodic patterns characterize numerous actual proteins: the rate at which similarity occurs between residues i and i + 4 or i + 7 or i + 11 is very often slightly higher than predicted by chance. That result could indicate that numerous actual proteins derive from ancestral clearcut periodic sequences. Nevertheless, it is shown that this recurrent periodic pattern occurs much more significantly when analyses are restricted to the alpha-helical portions of proteins while it never occurs when beta-stranded subsequences are taken into account. This preferential location of periodicity inside protein subregions corresponding to alpha helices suggests that the recurrent pattern of weak periodicity could result from an ubiquitous physical property of alpha helices. The regular alternation of hydrophobicity, which is most often displayed by alpha helices, could then be the origin of weak periodicity.
残基i与i + 4、i + 7或i + 11之间出现相似性的频率往往略高于随机预测的频率。这一结果可能表明，许多实际存在的蛋白质源自祖先明确的周期性序列。然而，研究表明，当分析仅限于蛋白质的α螺旋部分时，这种反复出现的周期性模式更为显著，而当考虑β链亚序列时则从未出现过。周期性在与α螺旋相对应的蛋白质子区域内的这种优先定位表明，微弱周期性的反复模式可能源于α螺旋普遍存在的物理特性。α螺旋最常表现出的疏水性的规则交替，可能就是微弱周期性的起源。
