Gleeson P A, Clarke A E
Biochem J. 1979 Sep 1;181(3):607-21. doi: 10.1042/bj1810607.
The major component of the Gladiolus style mucilage was shown to be an arabinogalactan-protein. The arabinogalactan-protein was isolated from the style extract by affinity chromatography with tridacnin (the galactose-binding lectin from the clam Tridacna maxima) coupled to Sepharose 4B. The isolated arabinogalactan-protein represents 40% of the soluble style extract; it contains 90% (w/w) carbohydrate and 3% protein. The major monosaccharides of the carbohydrate component are galactose and arabinose, in the proportions 6:1. A component with a similar composition was also isolated from the crude extract by precipitation with the beta-glucosyl artifical carbohydrate antigen. The protein moiety of the arabinogalactan-protein remained associated with the carbohydrate after chromatography in urea, and has high contents of serine, glutamic acid, aspartic acid, glycine and alanine. The arabinogalactan-protein is apparently chemically homogeneous; it eluted as a single symmetrical peak from Sepharose 4B, and three fractions collected across the peak were structurally similar. Ultracentrifugal studies showed it to be polydisperse in the mol.wt. range 150 000--400 000. The information obtained from methylation analyses, oxalic acid and enzymic hydrolyses is consistent with a model having a beta 1 leads to 3 galactan backbone, branched through C(O)6 to beta 1 leads to 6 galactan side chains. The arabinose is exclusively present as terminal alpha-L-arabinofuranosyl residues. Enzymic removal of the arabinose residues resulted in a marked decrease in solubility of the molecule. The localization of the arabinogalactan-protein in the mucilage of the style canal was demonstrated cytochemically. The possible roles of the arabinogalactan-protein in relation to recognition of compatible pollen and pollen-tube growth are discussed.
唐菖蒲花柱黏液的主要成分被证明是一种阿拉伯半乳聚糖蛋白。通过用与琼脂糖4B偶联的三角帆蚌凝集素（来自巨蛤三角帆蚌的半乳糖结合凝集素）进行亲和色谱法，从花柱提取物中分离出阿拉伯半乳聚糖蛋白。分离出的阿拉伯半乳聚糖蛋白占可溶性花柱提取物的40%；它含有90%（w/w）的碳水化合物和3%的蛋白质。碳水化合物成分的主要单糖是半乳糖和阿拉伯糖，比例为6:1。通过用β-葡糖基人工碳水化合物抗原沉淀，也从粗提取物中分离出了一种组成相似的成分。阿拉伯半乳聚糖蛋白的蛋白质部分在尿素中色谱分离后仍与碳水化合物结合，并且丝氨酸、谷氨酸、天冬氨酸、甘氨酸和丙氨酸的含量很高。阿拉伯半乳聚糖蛋白在化学上显然是均一的；它从琼脂糖4B上以单个对称峰洗脱，在峰上收集的三个馏分在结构上相似。超速离心研究表明它在分子量范围150 000 - 400 000内是多分散的。从甲基化分析、草酸和酶促水解获得的信息与具有β1→3半乳聚糖主链、通过C（O）6分支到β1→6半乳聚糖侧链的模型一致。阿拉伯糖仅以末端α-L-阿拉伯呋喃糖基残基的形式存在。酶促去除阿拉伯糖残基导致分子溶解度显著降低。通过细胞化学方法证明了阿拉伯半乳聚糖蛋白在花柱道黏液中的定位。讨论了阿拉伯半乳聚糖蛋白在识别亲和花粉和花粉管生长方面可能的作用。
