Gum arabic glycoprotein contains glycomodules of both extensin and arabinogalactan-glycoproteins
Gum arabic glycoprotein contains glycomodules of both extensin and arabinogalactan-glycoproteins
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DOI：
10.1016/s0031-9422(00)00043-1
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发表时间：
2000-05-01
期刊：
影响因子：
3.8
通讯作者：
Kieliszewski, MJ
中科院分区：
文献类型：
--
作者：
Goodrum, LJ;Patel, A;Kieliszewski, MJ
阿拉伯树胶糖蛋白（GAGP）是阿拉伯树胶中一种大分子量、富含羟脯氨酸的阿拉伯半乳聚糖蛋白（AGP）。GAGP具有简单、高度偏倚的氨基酸组成，表明重复的多肽骨架。以前的工作（Qi，W.，庞角，兰波特，D.T.A.，1991. Plant Physiology 96，848）提出了小的（类似于11个残基）重复肽基序，每个重复肽基序具有三个Hyp-arabinoside附着位点和一个Hyp-arabinogalactan多糖附着位点。我们通过HF去糖基化后GAGP多肽的序列分析来验证这一假设。一个密切相关的肽家族证实了重复的19个残基的共有基序的存在。然而，基序：Ser-Hyp-Hyp-Hyp-Thr-Leu-Ser-Hyp-Ser-Hyp-Thr-Hyp-Hyp约为预期大小的两倍。因此，根据GAGP的Hyp-glycoside谱判断，共有基序含有6个Hyp-arabinosides而不是3个，2个Hyp-polysaccharides而不是1个。我们基于Hyp邻接假设推断糖基化位点，该假设预测连续Hyp残基上的阿拉伯糖苷和成簇非连续Hyp残基上的阿拉伯半乳聚糖多糖，即GAGP基序将由两个中心Hyp-polysaccharide侧翼的阿拉伯糖基化连续Hyp块组成。我们预测，这使糖蛋白刚性化，增强了糖肽基序的整体对称性，并可能解释阿拉伯树胶的一些显着特性。(C)2000爱思唯尔科技有限公司版权所有。
Gum arabic glycoprotein (GAGP) is a large molecular weight, hydroxyproline-rich arabinogalactan-protein (AGP) component of gum arabic. GAGP has a simple, highly biased amino acid composition indicating a repetitive polypeptide backbone. Previous work (Qi, W., Pong, C., Lamport, D.T.A., 1991. Plant Physiology 96, 848), suggested small (similar to 11 residue) repetitive peptide motifs each with three Hyp-arabinoside attachment sites and a single Hyp-arabinogalactan polysaccharide attachment site. We tested that hypothesis by sequence analysis of the GAGP polypeptide after HF-deglycosylation. A family of closely related peptides confirmed the presence of a repetitive 19-residue consensus motif However, the motif: Ser-Hyp-Hyp-Hyp-Thr-Leu-Ser-Hyp-Ser-Hyp-Thr-Hyp-Thr-Hyp-Hyp was about twice the size anticipated. Thus, judging by Hyp-glycoside profiles of GAGP, the consensus motif contained six Hyp-arabinosides rather than three and two Hyp-polysaccharides rather than one. We inferred the glycosylation sites based on the Hyp contiguity hypothesis which predicts arabinosides on contiguous Hyp residues and arabinogalactan polysaccharides on clustered non-contiguous Hyp residues, i.e. the GAGP motif would consist of arabinosylated contiguous Hyp blocks flanking two central Hyp-polysaccharides. We predict this rigidifies the glycoprotein, enhances the overall symmetry of the glycopeptide motif, and may explain some of the remarkable properties of gum arabic. (C) 2000 Elsevier Science Ltd. All rights reserved.