STRUCTURAL ANALYSIS OF METHYLKETONE SYNTHASE 1

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 中等长度的甲基酮，如2-十三酮和2-十一酮，对许多草食性昆虫都有很强的毒性。2-十三酮和2-十一酮的产生最近被认为与α/β水解酶折叠蛋白家族的一个成员--甲基酮合成酶1(MKS1)的表达有关。MKS1是一种胞质定位蛋白，能够催化β-肉豆蔻酰-ACP脱酯为β-酮酸。含有α/β水解酶折叠的蛋白质序列几乎没有同源性，但在其活性部位确实具有保守的催化亲核、酸和组氨酸三联体。通常这些残基由丝氨酸、天冬氨酸和组氨酸组成。根据同样属于α/β水解酶超家族成员的羟腈裂解酶(HNL)对MKS1进行建模，显然MKS1不包含典型的催化三联体。得到了MKS_1晶体，并用HNL进行了分子置换，在2.3°分辨率下求解了其三维结构。从晶体结构来看，在MKS1活性中心内存在一个高度稳定的H2O分子，从而推测该H2O分子可能是MKS1中缺失的亲核试剂。为了解决所提出的机制，MKS1在与底物和/或产物的络合物中的高分辨率数据是必需的。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Medium length methylketones like 2-tridecanone and 2-undecanone are potent toxins to a number of herbivorous insects. The production of both 2-tridecanone and 2-undecanone was recently linked to the expression of a member of the alpha/beta hydrolase fold family of proteins, Methylketone Synthase 1 (MKS1). MKS1 is a plastid localized protein shown to catalyze the de-esterification of beta-myristoyl-ACP to beta-ketoacids. Proteins containing the alpha/beta hydrolase fold have little sequence identity but do possess a conserved catalytic triad of nucleophile, acid and a histidine in their active sites. Typically these residues consist of Ser, Asp, and His. Upon modeling MKS1 from Hydroxynitrile Lysase (HNL), also a member of the alpha/beta hydrolase superfamily, it was apparent that MKS1 did not contain the canonical catalytic triad. MKS1 crystals were obtained and the three dimensional structure was solved at 2.3 ¿ resolution by molecular replacement using HNL. From the crystal structure a highly stable H2O molecule was present within the MKS1 active site leading to the proposal that this H2O molecule could act as the nucleophile missing in MKS1. In order to address the proposed mechanism, higher resolution data of MKS1 in complex with substrate and or products is a requirement.