Fowler A V, Hediger M A, Musso R E, Zabin I
Biochimie. 1985 Jan;67(1):101-8. doi: 10.1016/s0300-9084(85)80235-2.
The amino acid sequence of thiogalactoside transacetylase, a dimer, has been determined. The monomer contains 202 amino acid residues in a single polypeptide chain and has a molecular weight of 22,671. The analysis was carried out by treatment of the carboxymethylated protein with cyanogen bromide and with trypsin. All seven cyanogen bromide peptides were isolated in pure form and were ordered by peptides isolated from tryptic digests. The sequence analysis was aided by determination of the DNA sequence of the lacA gene. The amino terminus of the protein is heterogenous because the initiator methionine is only partially cleaved. Another rather unusual feature of this cytoplasmic protein is a very hydrophobic segment in the center portion of the chain. Comparison of the amino acid sequence of thiogalactoside transacetylase to those of the lac repressor, beta-galactosidase, and lactose permease did not reveal any marked similarities. Therefore, there is no obvious evolutionary relatedness among proteins of the Lactose Operon.
硫代半乳糖苷转乙酰酶是一种二聚体，其氨基酸序列已被确定。单体在一条多肽链中含有202个氨基酸残基，分子量为22,671。分析是通过用溴化氰和胰蛋白酶处理羧甲基化蛋白来进行的。所有七个溴化氰肽都以纯形式分离出来，并通过从胰蛋白酶消化物中分离出的肽进行排序。通过测定lacA基因的DNA序列辅助进行序列分析。该蛋白质的氨基末端是异质的，因为起始甲硫氨酸仅被部分切割。这种细胞质蛋白的另一个相当不寻常的特征是在链的中心部分有一个非常疏水的片段。将硫代半乳糖苷转乙酰酶的氨基酸序列与乳糖阻遏物、β-半乳糖苷酶和乳糖通透酶的氨基酸序列进行比较，没有发现任何明显的相似性。因此，乳糖操纵子的蛋白质之间没有明显的进化相关性。
