Guenzi E, Galli G, Grgurina I, Gross D C, Grandi G
Department of Molecular Biology, Chiron S.p.A., Via Fiorentina, 1 53100 Siena, Italy.
J Biol Chem. 1998 Dec 4;273(49):32857-63. doi: 10.1074/jbc.273.49.32857.
With this work we have completed the characterization of the syringomycin synthetase gene cluster. In particular, by sequencing additional 28.5 kilobase pairs we show that the nine modules involved in the binding of the nine amino acids of syringomycin are localized on SyrB and SyrE, with SyrE carrying eight modules. The recombinant SyrB and the first and second modules of SyrE (SyrE1 and SyrE2) have been expressed in Escherichia coli and purified. The biochemical data indicate that SyrB binds threonine, the putative precursor of the last amino acid of syringomycin, whereas SyrE1 and SyrE2 bind serine, the first and the second amino acids of syringomycin, respectively. On the basis of the sequence analysis and the biochemical data presented here, it appears that syringomycin synthetase is unique among peptide synthetases in that its genetic organization does not respect the "colinearity rule" according to which the order of the amino acid binding modules along the chromosome parallels the order of the amino acids on the peptide. This feature, together with the absence of a single transcription unit and the absence of epimerase-like domains make syringomycin synthetase more related to the eukaryotic peptide synthetases than to the bacterial counterparts.
通过这项工作，我们完成了丁香霉素合成酶基因簇的表征。具体而言，通过对另外28.5千碱基对进行测序，我们发现参与丁香霉素九个氨基酸结合的九个模块位于SyrB和SyrE上，其中SyrE携带八个模块。重组SyrB以及SyrE的第一和第二个模块（SyrE1和SyrE2）已在大肠杆菌中表达并纯化。生化数据表明，SyrB结合苏氨酸，它是丁香霉素最后一个氨基酸的假定前体，而SyrE1和SyrE2分别结合丝氨酸，即丁香霉素的第一个和第二个氨基酸。根据此处提供的序列分析和生化数据，丁香霉素合成酶在肽合成酶中似乎是独特的，因为其基因组织不符合“共线性规则”，即沿着染色体的氨基酸结合模块的顺序与肽上氨基酸的顺序平行。这一特征，再加上缺乏单一转录单元以及没有类似差向异构酶的结构域，使得丁香霉素合成酶与真核肽合成酶的关系比与细菌肽合成酶的关系更为密切。
