Madison L L, Vivas E I, Li Y M, Walsh C T, Kolter R
Department of Molecular Genetics and Microbiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Mol Microbiol. 1997 Jan;23(1):161-8. doi: 10.1046/j.1365-2958.1997.2041565.x.
Microcin B17 (MccB17) is a ribosomally encoded DNA-gyrase inhibitor. Ribosomally encoded antibiotics are derived from precursors containing an N-terminal leader, which is removed during maturation, and a C-terminal structural peptide. PreMccB17, the translational product of mcbA, is modified into proMccB17 by the action of three enzymes, McbB, McbC, and McbD. A chromosomally encoded peptidase then converts proMccB17 into MccB17. The role of McbB, McbC, and McbD is to convert glycine, cysteine, and serine residues present in preMccB17 into four thiazole and four oxazole rings. Using a modification-specific antibody rather than antimicrobial activity, we show that the 26-amino-acid N-terminal leader of preMccB17 is essential for the conversion of preMccB17 into proMccB17. Neither a preMccB17 peptide lacking the leader nor a preMccB17-beta-galactosidase fusion lacking the leader are post-translationally modified.
微小菌素B17（MccB17）是一种核糖体编码的DNA解旋酶抑制剂。核糖体编码的抗生素来源于含有N端前导序列的前体，该前导序列在成熟过程中被去除，以及一个C端结构肽。前微小菌素B17（PreMccB17）是mcbA的翻译产物，在三种酶McbB、McbC和McbD的作用下被修饰为前体微小菌素B17（proMccB17）。一种染色体编码的肽酶随后将proMccB17转化为MccB17。McbB、McbC和McbD的作用是将PreMccB17中存在的甘氨酸、半胱氨酸和丝氨酸残基转化为四个噻唑环和四个恶唑环。使用一种修饰特异性抗体而非抗菌活性，我们发现PreMccB17的26个氨基酸的N端前导序列对于PreMccB17转化为proMccB17至关重要。既没有缺少前导序列的PreMccB17肽，也没有缺少前导序列的PreMccB17-β-半乳糖苷酶融合蛋白在翻译后被修饰。
