Characterization of the putative catalytic domain of two xyloglucan xylosyltransferases (XXTs) involved in the biosynthesis of xyloglucan in Arabidopsis thaliana

摘要: Xyloglucan is the primary hemicellulosic component of cell wall in dicotyledonous plants. It characterized by a β(1-4)-D-glucan backbone that substituted regular pattern with α(1-6)-D-xylose, and can be further β(1-2)-D-galactose or β(1-2)-D-galactose-α(1-2)-L-fucose disaccharide. Three xyloglucan xylosyltransferases (XXTs), XXT1, XXT2, XXT5, are responsible for D-xylosylation Arabidopsis thaliana. They Golgi-localized type II transmembrane proteins have putative DXD catalytic centers. All been shown to interact protein complex, XXT2 XXT5 showing strongest interaction, XXT1 demonstrated αD-xylosyltransferase (XT) activity vitro. The mechanism as well biological function still unknown. To study functional role motifs, AXA point mutants were made two motifs (DWD DSD) XXT5. N-terminal truncated versions these expressed E. coli vitro full-length stably transformed xxt knock-out A. thaliana their roles vivo. Results demonstrate both DWD DSD required Additionally, it was tXXT2-His could isolated >90% purity using native hybrid conditions exhibit XT activity. XXT5mut(1, 2, 12):xxt5 complemented transgenic plants generated, genotyped, phenotyped, analyzed expression, XyG content walls. results show mutations motif complement xxt5 phenotype while only partially complement,