Analysis of subunit interactions in the iterative type I polyketide synthase ATX from Aspergillus terreus
Analysis of subunit interactions in the iterative type I polyketide synthase ATX from Aspergillus terreus
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DOI：
10.1002/cbic.200600235
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发表时间：
2006-12-01
期刊：
影响因子：
3.2
通讯作者：
Fujii, Isao
中科院分区：
文献类型：
--
作者：
Moriguchi, Tomomi;Ebizuka, Yutaka;Fujii, Isao
芳香族聚酮化合物是由迭代型聚酮化合物脱氢酶（PKS）生物合成的。根据其结构，它们分为三种类型，I型，II型和III型。[1]III型PKS负责植物芳香族化合物如类黄酮和一些细菌化合物如1，3，6，8-四羟基萘。[2]大多数细菌芳香族聚酮是II型PKS系统的产物，其中独立的酮合酶（KS）亚基、α、β和酰基载体蛋白（ACP）反复联合收割机组合以构建聚酮碳骨架。[3]相比之下，真菌芳香族聚酮化合物是迭代I型PKS的产物，其至少由KS、酰基转移酶（AT）和ACP结构域组成，具有额外的催化结构域，如酮还原酶（KR）和克莱森环化酶（CYC），[4]都在单个多肽上。这些结构域参与重复的Claisen缩合以延长β-聚酮亚甲基中间体，然后通过羟醛和/或Claisen环化使其环化和芳构化。来自扩展青霉的MSAS是第一个被纯化至同质的PKS，[5]并且被发现是由188 kDa亚基组成的同源四聚体。[6]MSAS也是第一个被测序的真菌PKS。[7]从那时起，许多PKS基因已从真菌中克隆出来，并且由于真菌基因组计划的进展，真菌PKS的序列信息迅速增加。然而，很少有真菌PKS的功能已被确定的表达和产品鉴定的例子。[8]我们报道了从土曲霉中克隆的atX基因在带有α-淀粉酶启动子的真菌表达系统中的表达，并鉴定了ATX是一种MSAS。[9]ATX表达系统对6-甲基水杨酸（6-MSA）的高生产率使我们研究了其他真菌PKS的功能，如构巢曲霉WA，[10] Colletotrichum lagenarium PKS 1，[11]烟曲霉Alb 1 p，[12]和茄链格孢PKSN [13]和PKSF。[14]在那些功能已被鉴定的真菌PKS中，MSAS是尺寸最小的，由约190 kDa的多肽内的KS、AT、脱氢酶（DH）、KR和ACP结构域组成。MSAS的结构域组织与哺乳动物脂肪酸合酶（FAS）的结构域组织非常相似，al-
Aromatic polyketides are biosynthesized by iterative-type polyketide synthases (PKSs). Depending on their architecture, they are classified into three types, type I, II, and III.[1] Type III PKSs are responsible for plant aromatic compounds such as flavonoids and for some bacterial compounds such as 1, 3, 6, 8-tetrahydroxynaphthalene.[2] Most bacterial aromatic polyketides are products of type II PKS systems, in which independent ketosynthase (KS) subunits, α, β, and acyl carrier protein (ACP) combine iteratively to construct polyketide carbon skeletons.[3] In contrast, fungal aromatic polyketides are products of iterative type I PKSs, which consist of KS, acyltransferase (AT), and ACP domains as a minimum, with additional catalytic domains such as ketoreductase (KR) and Claisen cyclase (CYC),[4] all on single polypeptides. These domains are involved in repetitive Claisen condensations to elongate β-polyketomethylene intermediates, which are then cyclized and aromatized by aldol and/or Claisen cyclization.The best studied iterative type I aromatic PKS is the 6-methylsalicylic acid synthase (MSAS). The MSAS from Penicillium patulum was the first PKS to be purified to homogeneity,[5] and was found to be a homotetramer comprised of a 188 kDa subunit.[6] MSAS was also the first fungal PKS to be sequenced.[7] Since then, a number of PKS genes have been cloned from fungi, and sequence information on fungal PKSs is rapidly increasing because of the progress of fungal genome projects. However, there are few examples of fungal PKSs whose functions have been determined by expression and product identification.[8] We reported the expression of the atX gene cloned from Aspergillus terreus using a fungal expression system with an α-amylase promoter, and this experiment identified ATX to be a MSAS.[9] The high productivity of 6-methylsalicylic acid (6-MSA) by the ATX expression system led us to study functions of other fungal PKSs such as Aspergillus nidulans WA,[10] Colletotrichum lagenarium PKS1,[11] Aspergillus fumigatus Alb1p,[12] and Alternaria solani PKSN [13] and PKSF.[14] Of those fungal PKSs whose functions have been identified, MSAS is the smallest in size, consisting of KS, AT, dehydratase (DH), KR, and ACP domains within a polypeptide of approximately 190kDa. The domain organization of MSAS is quite similar to that of mammalian fatty acid synthase (FAS), al-