Intron positions correlate with module boundaries in ancient proteins
Intron positions correlate with module boundaries in ancient proteins
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DOI：
10.1073/pnas.93.25.14632
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发表时间：
1996-12-10
影响因子：
11.1
通讯作者：
Gilbert, W
中科院分区：
文献类型：
--
作者：
deSouza, SJ;Long, M;Gilbert, W
我们通过计算机程序分析蛋白质的三维结构，该程序发现包含模块边界的序列区域，将模块定义为在空间中以特定给定距离为界的pol肽链的一段，该程序定义了一组“连接区”，其具有以下性质：如果将内含子置于每个连接区中，蛋白质将被切割成一组均小于指定直径的模块。我们测试了一组32个蛋白质，所有的古代起源，和相应的一组570个内含子的位置，询问是否有一个统计学上显着过量的内含子的位置内的接头区域。对于28埃模块，历史上使用的标准尺寸，我们发现这种过度，P < 0.003。这种相关性既不是由于连接区中的组成或序列偏差，也不是由于内含子位置的表面偏差。此外，可以推定为旧的20个内含子的子集更明确地位于连接区内，P < 0.0003，因此，如内含子早期方法所预期的那样，内含子位置和古蛋白质的三维结构元件之间存在强相关性，然后，我们研究了一系列的模块直径，并表明，随着直径的变化，相关性的显着峰值出现为中心的模块直径在21.7，27.6，和32.9埃。这些优选的模块直径大致对应于预测的外显子大小15、22和30个残基。因此，内含子、模块和多肽链长度的量化模式之间存在显著的相关性，这是基因外显子理论的预测。''
We analyze the three-dimensional structure of proteins by a computer program that finds regions of sequence that contain module boundaries, defining a module as a segment of pol peptide chain bounded in space by a specific given distance, The program defines a set of ''linker regions'' that have the property that if an intron were to be placed into each linker region, the protein would be dissected into a set of modules all less than the specified diameter. We test a set of 32 proteins, all of ancient origin, and a corresponding set of 570 intron positions, to ask if there is a statistically significant excess of intron positions within the linker regions. For 28-Angstrom modules, a standard size used historically, we find such an excess, with P < 0.003. This correlation is neither due to a compositional or sequence bias in the linker regions nor to a surface bias in intron positions, Furthermore, a subset of 20 introns, which can be putatively identified as old, lies even more explicitly within the linker regions, with P < 0.0003, Thus, there is a strong correlation between intron positions and three-dimensional structural elements of ancient proteins as expected by the introns-early approach, We then study a range of module diameters and show that, as the diameter varies, significant peaks of correlation appear for module diameters centered at 21.7, 27.6, and 32.9 Angstrom. These preferred module diameters roughly correspond to predicted exon sizes of 15, 22, and 30 residues, Thus, there are significant correlations between introns, modules, and a quantized pattern of the lengths of polypeptide chains, which is the prediction of the ''Exon Theory of Genes.''