Fachbereich Biologie der Universität Kaiserslautern, 6750 Kaiserslautern, Federal Republic of Germany.
Plant Physiol. 1982 Mar;69(3):678-81. doi: 10.1104/pp.69.3.678.
A crude membrane fraction from Chlamydomonas reinhardii was found to catalyze d-galactose transfer from UDP-galactose to endogenous proteins. Highest incorporation rates were achieved by incubation at 25 degrees C and pH 7.5 in the presence of 10 millimolar Fe(2+). Hydrolytic studies on the labeled polymer revealed that radioactivity was attached to protein via an alkali-stable and acid-labile linkage. Identification of galactose as the only labeled sugar in the acid hydrolysate and results of a tentative estimation of the molecular weight of the charged alkaline degradation product indicate that monomeric galactose units are transferred to form an O-glycosidic bond with peptidyl hydroxyproline. No indications were found for a similar linkage to serine which, in contrast to the hydroxyproline-O-glycoside linkage, is acid-stable but is cleaved by beta-elimination. Chromatography of the sodium dodecyl sulfate-solubilized polymer on Sepharose-6B demonstrated that galactosyl residues are mainly associated with proteins which are of considerably higher molecular weight than are the majority of sodium dodecyl sulfate-denatured membrane proteins in this fraction.
从莱茵衣藻中提取的粗膜级分被发现能够催化 UDP-半乳糖向内源性蛋白质的转移。在 25°C 和 pH7.5 条件下,在 10 毫摩尔 Fe(2+)存在下,可达到最高的掺入速率。对标记聚合物的水解研究表明,放射性物质通过一种耐碱、易酸的键与蛋白质结合。在酸水解物中仅鉴定出半乳糖是标记的糖,以及对带电荷的碱性降解产物的分子量进行的初步估计的结果表明,单体半乳糖单元被转移以与肽基羟脯氨酸形成 O-糖苷键。没有发现与丝氨酸类似的键,与羟脯氨酸-O-糖苷键相反,丝氨酸-O-糖苷键耐酸但可通过β-消除切割。SDS 可溶性聚合物在 Sepharose-6B 上的色谱分析表明,半乳糖残基主要与蛋白质结合,这些蛋白质的分子量明显高于该级分中大多数 SDS 变性的膜蛋白。