Boekhorst Jos, Helmer Quinta, Kleerebezem Michiel, Siezen Roland J
Centre for Molecular and Biomolecular Informatics, Radboud University Nijmegen, 6525ED, Nijmegen, The Netherlands.
NIZO food research, Ede, The Netherlands.
Microbiology (Reading). 2006 Jan;152(Pt 1):273-280. doi: 10.1099/mic.0.28415-0.
Lactic acid bacteria (LAB) are frequently encountered inhabitants of the human intestinal tract. A protective layer of mucus covers the epithelial cells of the intestine, offering an attachment site for these bacteria. In this study bioinformatics tools were used to identify and characterize proteins containing one type of mucus-binding domain, called MUB, that is postulated to play an important role in the adherence of LAB to this mucus layer. By searching in all protein databases 48 proteins containing at least one of these MUB domains in nine LAB species were identified. These MUB domains varied in size, ranging from approximately 100 to more than 200 residues per domain. Complete MUB domains were found exclusively in LAB. The number of MUB domains present in a single protein varied from 1 to 15. In some cases, orthologous proteins in closely related species contained a different number of domains, indicating that repeats of the domain undergo rapid duplication and deletion. Proteins containing the MUB domain were often encoded by gene clusters that encode multiple extracellular proteins. In addition to one or more copies of the MUB domain, many of these proteins contained other domains that are predicted to be involved in binding to and degradation of extracellular components. These findings strongly suggest that the MUB domain is an LAB-specific functional unit that performs its task in various domain contexts and could fulfil an important role in host-microbe interactions in the gastrointestinal tract.
乳酸菌（LAB）是人类肠道中常见的寄居菌。一层保护性的黏液覆盖着肠道上皮细胞，为这些细菌提供了附着位点。在本研究中，利用生物信息学工具来鉴定和表征含有一种黏液结合结构域（称为MUB）的蛋白质，据推测该结构域在乳酸菌黏附于该黏液层中发挥重要作用。通过在所有蛋白质数据库中搜索，在9种乳酸菌中鉴定出48种含有至少一个此类MUB结构域的蛋白质。这些MUB结构域大小各异，每个结构域约含100至200多个残基。完整的MUB结构域仅在乳酸菌中发现。单个蛋白质中存在的MUB结构域数量从1到15不等。在某些情况下，亲缘关系密切的物种中的直系同源蛋白质含有不同数量的结构域，这表明该结构域的重复会经历快速的复制和缺失。含有MUB结构域的蛋白质通常由编码多种细胞外蛋白质的基因簇编码。除了一个或多个MUB结构域拷贝外，这些蛋白质中的许多还含有其他结构域，预计这些结构域参与细胞外成分的结合和降解。这些发现强烈表明，MUB结构域是乳酸菌特有的功能单元，在各种结构域环境中执行其任务，并且可能在胃肠道的宿主-微生物相互作用中发挥重要作用。
