Structure and function of family 1 glycosyltransferases

描述（由申请人提供）：ndp -糖基转移酶对所有复杂碳水化合物和糖缀合物的生物合成至关重要。这种种类繁多的酶催化糖单位转移到目标化合物上，从而在植物、动物和细菌中产生一系列不同的大分子：糖脂、脂多糖、植物中的聚糖结构、糖蛋白和具有生物医学重要性的糖基化天然产物，如抗生素、激素、抗肿瘤药物和心脏糖苷。首先，我们打算确定家族1 ndp糖基转移酶（GTFs）的3个亚家族的x射线晶体结构：参与万古霉素类抗生素生物合成的GTFs，产生甾醇糖苷的GTFs，以及参与二酰基甘油糖基化的两个GTFs。我们的目标是阐明(1)ndp -糖识别的物理基础，(2)苷元受体识别的物理基础，以及(3)糖基转移的机制。了解这些酶的结构多样性将增强我们对糖生物学的理解，特别是关于糖脂、糖类固醇和抗生素的生物合成。更好地了解次生代谢物的糖基化也将为针对致病性生物的抗生素设计和其他生物医学相关化合物（例如，心脏苷或抗肿瘤药物）的设计开辟新的途径。家族1 ndp -糖基转移酶在物种之间的同源酶以及物种内类似酶之间显示出显著的功能保守性，尽管在许多情况下氨基酸序列保守性非常低（通常小于25%）。最近的研究也发现了在这个功能类的所有成员之间保守的结构同源性的不同元素。通过比较蛋白质序列分析，1家族酶的结构数据库可以对该家族中任何结构未知的蛋白质进行建模。此外，家族1 ndp -糖基转移酶相对简单的双结构域设计为设计具有新功能的嵌合酶提供了可能性。混合杂化酶设计与组合生物合成可以为生产具有生物医学意义的新型糖缀合物提供实用的途径。

DESCRIPTION (provided by applicant): NDP-sugar glycosyltransferases are critical for the biosynthesis of all complex carbohydrates and glycoconjugates. This large and diverse class of enzymes catalyzes the transfer of saccharide units onto the target compounds to create a diverse set of macromolecules in plants, animals, and bacteria: glycolipids, lipopolysaccharides, the glycan structures in plants, glycoproteins, and glycosylated natural products of biomedical importance like antibiotics, hormones, antitumor agents, and cardiac glycosides. Initially, we intend to determine the X-ray crystal structures of 3 subfamilies of the family 1 NDP-sugar glycosyltransferases (GTFs): GTFs involved in the biosynthesis of vancomycin group antibiotics, GTFs which create sterol glucosides, and two GTFs involved in the glycosylation of diacylglycerol. Our goals are to elucidate (1) the physical basis for the recognition of NDP-sugars, (2) the physical basis for the recognition of the aglycone acceptors, and (3) the mechanism of glycosyltransfer. Understanding the structural diversity of these enzymes will enhance our understanding of glycobiology, particularly regarding the biosynthesis of glycolipids, glycosteroids, and antibiotics. A better understanding of the glycosylation of secondary metabolites will also open up new avenues for antibiotic design against pathogenic organisms and the design of other biomedically relevant compounds (e.g., cardiac glycosides or antitumor agents). Family 1 NDP-sugar glycosyltransferases show significant conservation of functionality among homologous enzymes across species as well as between analogous enzymes within a species, despite very low levels of amino acid sequence conservation (often <25% identity) in many cases. Recent research has also detected distinct elements of structural homology that are conserved between all members of this functional class. With comparative protein sequence analysis, a structural database of the family 1 enzyme could allow the modeling of any structurally unknown protein within this family. Moreover, the relatively simple bi-domain design of family 1 NDP-sugar glycosyltransferases raises the possibility of designing chimeric enzymes with novel functionalities. Mixing hybrid enzyme design with combinatorial biosynthesis could provide practical ways to produce new glycoconjugates of biomedical importance.