National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.
Biol Direct. 2010 Jan 7;5:1. doi: 10.1186/1745-6150-5-1.
Eukaryotic extracellular matrices such as proteoglycans, sclerotinized structures, mucus, external tests, capsules, cell walls and waxes contain highly modified proteins, glycans and other composite biopolymers. Using comparative genomics and sequence profile analysis we identify several novel enzymes that could be potentially involved in the modification of cell-surface glycans or glycoproteins.
Using sequence analysis and conservation we define the acyltransferase domain prototyped by the fungal Cas1p proteins, identify its active site residues and unify them to the superfamily of classical 10TM acyltransferases (e.g. oatA). We also identify a novel family of esterases (prototyped by the previously uncharacterized N-terminal domain of Cas1p) that have a similar fold as the SGNH/GDSL esterases but differ from them in their conservation pattern.
We posit that the combined action of the acyltransferase and esterase domain plays an important role in controlling the acylation levels of glycans and thereby regulates their physico-chemical properties such as hygroscopicity, resistance to enzymatic hydrolysis and physical strength. We present evidence that the action of these novel enzymes on glycans might play an important role in host-pathogen interaction of plants, fungi and metazoans. We present evidence that in plants (e.g. PMR5 and ESK1) the regulation of carbohydrate acylation by these acylesterases might also play an important role in regulation of transpiration and stress resistance. We also identify a subfamily of these esterases in metazoans (e.g. C7orf58), which are fused to an ATP-grasp amino acid ligase domain that is predicted to catalyze, in certain animals, modification of cell surface polymers by amino acid or peptides.
This article was reviewed by Gaspar Jekely and Frank Eisenhaber.
真核细胞外基质，如蛋白聚糖、矿化结构、黏液、外壳、胶囊、细胞壁和蜡质，含有高度修饰的蛋白质、聚糖和其他复合生物聚合物。利用比较基因组学和序列谱分析，我们鉴定出几种可能参与细胞表面糖链或糖蛋白修饰的新酶。
利用序列分析和保守性，我们定义了真菌 Cas1p 蛋白原型的酰基转移酶结构域，鉴定了其活性位点残基，并将其统一到经典 10TM 酰基转移酶超家族（如 oatA）中。我们还鉴定了一个新的酯酶家族（由 Cas1p 以前未被表征的 N 端结构域原型），它们具有与 SGNH/GDSL 酯酶相似的折叠，但在保守模式上与它们不同。
我们假设酰基转移酶和酯酶结构域的联合作用在控制聚糖的酰化水平方面起着重要作用，从而调节它们的物理化学性质，如吸湿性、抗酶水解性和物理强度。我们提出的证据表明，这些新酶对聚糖的作用可能在植物、真菌和后生动物的宿主-病原体相互作用中发挥重要作用。我们提出的证据表明，在植物中（如 PMR5 和 ESK1），这些酰基酯酶对碳水化合物酰化的调节也可能在调节蒸腾和抗应激方面发挥重要作用。我们还在后生动物中鉴定出这些酯酶的一个亚家族（如 C7orf58），它们与一个 ATP-抓取氨基酸连接酶结构域融合，该结构域预计在某些动物中催化通过氨基酸或肽修饰细胞表面聚合物。
这篇文章由 Gaspar Jekely 和 Frank Eisenhaber 进行了评论。
