Computational Systems Biology Laboratory and Institute of Bioinformatics, University of Georgia, Athens, Georgia 30602, USA.
Plant Physiol. 2010 Aug;153(4):1729-46. doi: 10.1104/pp.110.154229. Epub 2010 Jun 3.
Carbohydrate-active enzyme glycosyltransferase family 8 (GT8) includes the plant galacturonosyltransferase1-related gene family of proven and putative alpha-galacturonosyltransferase (GAUT) and GAUT-like (GATL) genes. We computationally identified and investigated this family in 15 fully sequenced plant and green algal genomes and in the National Center for Biotechnology Information nonredundant protein database to determine the phylogenetic relatedness of the GAUTs and GATLs to other GT8 family members. The GT8 proteins fall into three well-delineated major classes. In addition to GAUTs and GATLs, known or predicted to be involved in plant cell wall biosynthesis, class I also includes a lower plant-specific GAUT and GATL-related (GATR) subfamily, two metazoan subfamilies, and proteins from other eukaryotes and cyanobacteria. Class II includes galactinol synthases and plant glycogenin-like starch initiation proteins that are not known to be directly involved in cell wall synthesis, as well as proteins from fungi, metazoans, viruses, and bacteria. Class III consists almost entirely of bacterial proteins that are lipooligo/polysaccharide alpha-galactosyltransferases and alpha-glucosyltransferases. Sequence motifs conserved across all GT8 subfamilies and those specific to plant cell wall-related GT8 subfamilies were identified and mapped onto a predicted GAUT1 protein structure. The tertiary structure prediction identified sequence motifs likely to represent key amino acids involved in catalysis, substrate binding, protein-protein interactions, and structural elements required for GAUT1 function. The results show that the GAUTs, GATLs, and GATRs have a different evolutionary origin than other plant GT8 genes, were likely acquired from an ancient cyanobacterium (Synechococcus) progenitor, and separate into unique subclades that may indicate functional specialization.
碳水化合物活性酶糖基转移酶家族 8（GT8）包括已证实和推测的α-半乳糖基转移酶（GAUT）和 GAUT 样（GATL）基因的植物半乳糖基转移酶 1 相关基因家族。我们通过计算方法在 15 个完全测序的植物和绿藻基因组以及美国国家生物技术信息中心非冗余蛋白质数据库中鉴定和研究了这个家族，以确定 GAUT 和 GATL 与其他 GT8 家族成员的系统发育关系。GT8 蛋白分为三个明显不同的主要类群。除了 GAUT 和 GATL，已知或推测参与植物细胞壁生物合成的，I 类还包括一个低等植物特有的 GAUT 和 GATL 相关（GATR）亚家族，两个后生动物亚家族，以及来自其他真核生物和蓝藻的蛋白质。II 类包括半乳糖醇合酶和植物糖原合酶样淀粉起始蛋白，它们不被认为直接参与细胞壁合成，以及来自真菌、后生动物、病毒和细菌的蛋白质。III 类几乎完全由细菌蛋白组成，这些蛋白是脂寡糖/多糖α-半乳糖基转移酶和α-葡萄糖基转移酶。鉴定并映射到预测的 GAUT1 蛋白质结构上了所有 GT8 亚家族保守的序列基序和那些与植物细胞壁相关的 GT8 亚家族特有的序列基序。三级结构预测确定了可能代表参与催化、底物结合、蛋白质-蛋白质相互作用以及 GAUT1 功能所需结构元件的关键氨基酸的序列基序。结果表明，GAUT、GATL 和 GATR 与其他植物 GT8 基因具有不同的进化起源，可能来自古老的蓝细菌（蓝藻）祖先，并分离成独特的亚群，这可能表明功能特化。
