Raval Sujana, Gowda Sharan B, Singh Desh D, Chandra Nagasuma R
Bioinformatics Centre, Indian Institute of Science, Bangalore 560 012, India.
Glycobiology. 2004 Dec;14(12):1247-63. doi: 10.1093/glycob/cwh140. Epub 2004 Aug 25.
Lectins are known to be important for many biological processes, due to their ability to recognize cell surface carbohydrates with high specificity. Plant lectins have been model systems to study protein-carbohydrate recognition, because individually they exhibit high sensitivity and as a group large diversity in recognizing carbohydrate structures. Although extensive studies have been carried out for legume lectins that have led to interesting insights into the sequence determinants of sugar recognition in them, frameworks with such specific correlations are not available for other plant lectin families. This study reports a large-scale data acquisition and extensive analysis of sequences and structures of beta-prism-I or jacalin-related lectins (JRLs) and shows that hypervariability in the binding site loops generates carbohydrate recognition diversity, a strategy analogous to that in legume lectins. Analyses of the size, conformation, and sequence variability in key regions reveal the existence of a common theme, encoded as a set of structural features over a common scaffold, in defining specificity. This study also points to the remarkable range of domain architectures, often arising out of gene duplication events in lectins of this family. The data analyzed here also indicate a spectacular variety of quaternary associations possible in this family of lectins that have implications for glycan recognition. These results thus provide sequence-structure-function correlations, an understanding of the molecular basis of carbohydrate recognition by beta-prism-I lectins, and also a rationale for engineering specific recognition capabilities in relevant molecules.
由于凝集素能够高度特异性地识别细胞表面碳水化合物，因此它们在许多生物学过程中都起着重要作用。植物凝集素一直是研究蛋白质 - 碳水化合物识别的模型系统，因为它们各自表现出高灵敏度，并且作为一个整体在识别碳水化合物结构方面具有很大的多样性。尽管已经对豆科植物凝集素进行了广泛研究，并对其中糖识别的序列决定因素有了有趣的见解，但其他植物凝集素家族尚无具有这种特定相关性的框架。本研究报告了对β-棱柱-I或jacalin相关凝集素（JRLs）的序列和结构进行的大规模数据采集和广泛分析，结果表明结合位点环的高变异性产生了碳水化合物识别多样性，这一策略类似于豆科植物凝集素中的策略。对关键区域的大小、构象和序列变异性分析揭示了在定义特异性方面存在一个共同主题，该主题编码为在一个共同支架上的一组结构特征。本研究还指出了该家族凝集素中常常由基因复制事件产生的显著的结构域结构范围。这里分析的数据还表明，该家族凝集素中可能存在各种各样的四级缔合，这对聚糖识别有影响。因此，这些结果提供了序列 - 结构 - 功能相关性，有助于理解β-棱柱-I凝集素识别碳水化合物的分子基础，也为在相关分子中设计特定识别能力提供了理论依据。
