Squires C H, De Felice M, Devereux J, Calvo J M
Nucleic Acids Res. 1983 Aug 11;11(15):5299-313. doi: 10.1093/nar/11.15.5299.
ilvIH of Escherichia coli K12 codes for a valine-sensitive acetohydroxy acid synthase (AHASIII). The DNA sequence of ilvIH was determined. Open reading frames and appropriate translation signals exist for two polypeptides, one containing 565 amino acids (ilvI polypeptide) and the other 160 amino acids (ilvH polypeptide). A graphic matrix analysis shows three clearcut regions of homology between ilvI and ilvG (codes for AHASII). Within these three regions of homology, 50-60% of the amino acid sequences of AHASII and AHASIII are conserved. Inspection of the region between ilvG and ilvE (the K region) revealed that it can potentially code for an 86 amino acid polypeptide. A computer analysis shows small but significant homology between the predicted amino acid sequences of the N-terminal half of the ilvH polypeptide and the putative region K polypeptide. We conclude that ilvIH and ilvG-region K evolved from a common ancestor.
大肠杆菌K12的ilvIH编码一种对缬氨酸敏感的乙酰羟酸合酶（AHASIII）。测定了ilvIH的DNA序列。存在两个多肽的开放阅读框和适当的翻译信号，一个含有565个氨基酸（ilvI多肽），另一个含有160个氨基酸（ilvH多肽）。图形矩阵分析显示ilvI和ilvG（编码AHASII）之间有三个明显的同源区域。在这三个同源区域内，AHASII和AHASIII的氨基酸序列有50-60%是保守的。对ilvG和ilvE之间的区域（K区域）进行检查发现，它可能编码一种86个氨基酸的多肽。计算机分析表明，ilvH多肽N端一半的预测氨基酸序列与假定的区域K多肽之间存在微小但显著的同源性。我们得出结论，ilvIH和ilvG区域K是由一个共同祖先进化而来的。
