圈卷产色链霉菌尼可霉素生物合成基因——sanH和sanI的研究

通过反向遗传学方法克隆到圈卷产色链霉菌尼可霉素生物合成基因簇中约7.0kb的DNA片段。该片段除含有尼可霉素生物合成基因sanF外，对sanF上游约22kb的BglⅡDNA片段进行序列测定及分析表明，还含有两个完整的开放阅读框(ORF)。ORF1由1233个核苷酸组成，ORF2由195个核苷酸组成，它们分别编码由410个氨基酸残基和64个氨基酸残基组成的蛋白质，依次命名为sanH和sanI。蛋白序列数据库比较结果表明，SanH和SanI与浅灰链霉菌(\%Streptomyces griseolus)\%中共转录的细胞色素P450(cytochrome P450)和铁氧还蛋白(ferredoxin)有较高的同源性，一致性分别为46%和56%，相似性分别为62%和70%。基因功能研究表明，sanH基因的破坏虽不影响圈卷产色链霉菌产生的尼可霉素的生物活性，但该基因可能参与了尼可霉素羟基化反应的生物合成。

STUDIES ON sanH AND sanI--GENES RELATED TO NIKKOMYCIN BIOSYNTHESIS OF STREPTOMYCES ANSOCHROMOGENES

A 7.0 kb DNA fragment was cloned by reverse genetics, which was located in the gene cluster of nikkomycin biosynthesis of Streptomyces ansochromogenes. Besides sanF--a gene related to nikkomycin biosynthesis of S. ansochromogenes, the sequence of a 2.2 kb BglII DNA fragment upstream sanF was determined. This 2.2 kb DNA fragment cointains two complete open reading frames (ORF). ORF1 consists of 1233 base pairs, ORF2 consistis of 195 base pairs, and they encode proteins with 410 amino acids and 64 amino acids respectively, which were designated as sanH and sanI. In search of databases, the deduced products of sanH has 46% amino acid identities and 62% amino acid similarities in comparison with the cytochrome P450 of Streptomyces griseolus, and the deduced protein of sanI has 56% amino acid identities and 70% amino acid similarities with the ferredoxin of S. griseolus. The function of sanH gene was studied using strategy of gene disruption, and the result showed that the disruption of sanH didn't influence nikkomycin biological activity in S. ansochromogenes.