THE ASPERGILLUS-PARASITICUS POLYKETIDE SYNTHASE GENE PKSA, A HOMOLOG OF ASPERGILLUS-NIDULANS WA, IS REQUIRED FOR AFLATOXIN B-1 BIOSYNTHESIS
THE ASPERGILLUS-PARASITICUS POLYKETIDE SYNTHASE GENE PKSA, A HOMOLOG OF ASPERGILLUS-NIDULANS WA, IS REQUIRED FOR AFLATOXIN B-1 BIOSYNTHESIS
复制标题
DOI：
10.1007/bf02191593
复制
发表时间：
1995-08-21
期刊：
影响因子：
--
通讯作者：
CLEVELAND, TE
中科院分区：
文献类型：
--
作者：
CHANG, PK;CARY, JW;CLEVELAND, TE
黄曲霉毒素包括一组由寄生曲霉和黄曲霉产生的聚酮衍生的致癌真菌毒素。通过pXX破坏构建体的转化，我们破坏了a . parasiticus SRRC 2043的黄曲霉毒素途径，导致该菌株无法产生黄曲霉毒素中间体以及转化体中的一种主要黄色色素。这种破坏归因于pXX与寄主寄生蜂基因组在特定位点pksA上的单次交叉同源整合事件。序列分析表明，pksA与细粒曲霉（Aspergillus nidulans） wA基因同源，wA基因是参与分生孢子壁色素生物合成的聚酮合成酶基因。导出的pksA产物氨基酸序列中存在保守的β -酮酰合成酶、酰基转移酶和酰基载体蛋白结构域。没有发现β -酮酰还原酶和烯酰还原酶结构域，这表明pksA不编码加工β -碳的催化活性，类似于长链脂肪酸合成所需的催化活性。pksA基因位于黄曲霉毒素通路基因簇中，与nor-1基因相连；一种黄曲霉毒素途径基因，用于将去盐酸转化为averantin。这两个基因从1.5 kb的基因间区发散转录。我们认为pksA是黄曲霉毒素生物合成早期所需的聚酮合成酶基因。
Aflatoxins comprise a group of polyketide-derived carcinogenic mycotoxins produced by Aspergillus parasiticus and Aspergillus flavus. By transformation with a disruption construct, pXX, we disrupted the aflatoxin pathway in A. parasiticus SRRC 2043, resulting in the inability of this strain to produce aflatoxin intermediates as well as a major yellow pigment in the transformants. The disruption was attributed to a single-crossover, homologous integration event between pXX and the recipient A. parasiticus genome at a specific locus, designated pksA. Sequence analysis suggest that pksA is a homolog of the Aspergillus nidulans wA gene, a polyketide synthase gene involved in conidial wall pigment biosynthesis. The conserved beta-ketoacyl synthase, acyltransferase and acyl carrier-protein domains were present in the deduced amino acid sequence of the pksA product. No beta-ketoacyl reductase and enoyl reductase domains were found, suggesting that pksA does not encode catalytic activities for processing beta-carbon similar to those required for long chain fatty acid synthesis. The pksA gene is located in the aflatoxin pathway gene cluster and is linked to the nor-1 gene; an aflatoxin pathway gene required for converting norsolorinic acid to averantin. These two genes are divergently transcribed from a 1.5 kb intergenic region. We propose that pksA is a polyketide synthase gene required for the early steps of aflatoxin biosynthesis.