Organization of the biosynthetic gene cluster for rapamycin in Streptomyces hygroscopicus: Analysis of the enzymatic domains in the modular polyketide synthase
Organization of the biosynthetic gene cluster for rapamycin in Streptomyces hygroscopicus: Analysis of the enzymatic domains in the modular polyketide synthase
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DOI：
10.1016/0378-1119(95)00800-4
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发表时间：
1996-02-22
期刊：
影响因子：
3.5
通讯作者：
Leadlay, PF
中科院分区：
文献类型：
--
作者：
Aparicio, JF;Molnar, I;Leadlay, PF
雷帕霉素产生聚酮合成酶的三个巨型多功能多肽(RAPS1、RAPS2和RAPS3)最近被证明包含14个独立的酶活性组或模块，每个模块催化一轮特定的聚酮链延伸。这些蛋白质模块之间的详细序列比较使得对AA的进一步表征在催化或特异性方面可能是重要的。酰基载体蛋白(ACP)、β-酮酰基-ACP合成酶(KS)和酰基转移酶(AT)结构域(核心区)具有极高的序列同源性。尤其是KS结构域在其全长上几乎是完美的重复，模块14显示的同源性最低，并且唯一的是只具有核心域，即使在某些模块中也存在烯醇酰还原酶(ER)、β-酮酰基-ACP还原酶(KR)和脱水酶(DH)结构域，通过活性位点序列中的特征缺失可以识别四个水解域为非活性，但对于另外两个，并且对于模块3中的KR和ER，该序列与其他模块中的活性对应的序列无法区分。RAPS1的N末端含有一个新的辅酶A连接酶(CL)结构域，它激活并连接由莽草酸衍生的起始单元，以及一个可以在连接后修改起始单元的ER活性。序列比较发现，结构域之间的‘连接’区域之间有惊人的高序列相似性，并且在每个多酶亚基的N末端还有一个潜在的两亲性螺旋，这可能促进二聚成活性物种。
The three giant multifunctional polypeptides of the rapamycin (Rp)-producing polyketide synthase (RAPS1, RAPS2 and RAPS3) have recently been shown to contain 14 separate sets, or modules, of enzyme activities, each module catalysing a specific round of polyketide chain extension. Detailed sequence comparison between these protein modules has allowed further characterisation of aa that may be important in catalysis or specificity. The acyl-carrier protein (ACP), beta-ketoacyl-ACP synthase (KS) and acyltransferase (AT) domains (the core domains) have an extremely high degree of mutual sequence homology. The KS domains in particular are almost perfect repeats over their entire length, Module 14 shows the least homology and is unique in possessing only core domains, The enoyl reductase (ER), beta-ketoacyl-ACP reductase (KR) and dehydratase (DH) domains are present even in certain modules where they are not apparently required, Four DH domains can be recognised as inactive by characteristic deletions in active site sequences, but for two others, and for KR and ER in module 3, the sequence is not distinguishable from that of active counterparts in other modules. The N terminus of RAPS1 contains a novel coenzyme A ligase (CL) domain that activates and attaches the shikimate-derived starter unit, and an ER activity that may modify the starter unit after attachment, The sequence comparison has revealed the surprisingly high sequence similarity between inter-domain 'linker' regions, and also a potential amphipathic helix at the N terminus of each multienzyme subunit which may promote dimerisation into active species.