STRUCTURAL ANALYSIS OF METHYLKETONE SYNTHASE 1

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 中等长度的甲基酮如2-十三酮和2-十一酮是对许多食草昆虫的强效毒素。2-十三烷酮和2-十一烷酮的产生最近与α/β水解酶折叠蛋白家族的成员甲基酮合成酶1（MKS 1）的表达有关。MKS 1是一种质体定位蛋白，可催化β-肉豆蔻酰-ACP脱酯化为β-酮酸。含有α/β水解酶折叠的蛋白质具有很小的序列同一性，但在其活性位点具有亲核体、酸和组氨酸的保守催化三联体。通常这些残基由Ser、Asp和His组成。在从羟基腈裂解酶（HNL）（也是α/β水解酶超家族的成员）建模MKS 1时，很明显MKS 1不包含典型的催化三联体。获得MKS 1晶体，并通过使用HNL的分子置换以2.3分辨率解析三维结构。根据晶体结构，MKS 1活性位点内存在高度稳定的H2O分子，这导致提出该H2O分子可以充当MKS 1中缺失的亲核试剂。为了解决所提出的机制，需要MKS 1与底物和/或产物复合的更高分辨率数据。

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 Sythase 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 deminsional 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.