State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
Int J Mol Sci. 2022 Apr 8;23(8):4136. doi: 10.3390/ijms23084136.
Xylanase releases xylo-oligosaccharides from dietary xylan, which stimulate the growth of the gut bacteria lactobacilli. Many lactobacilli adhere to dietary fibers, which may facilitate the assimilation of xylo-oligosaccharides and help them gain competence in the gut, but the underlying mechanisms remain elusive. Herein we report, from the highly abundant transcripts of cultured in wheat arabinoxylan supplemented with a xylanase, the identification of genes encoding four putative cell-surface WxL proteins (Lb630, Lb631, Lb632, and Lb635) and one S-layer protein (Lb1325) with either cellulose- or xylan-binding ability. The repetitively occurring WxL proteins were encoded by a gene cluster, among which Lb630 was chosen for further mutational studies. The analysis revealed three aromatic residues (F30, W61, and W156) that might be involved in the interaction of the protein with cellulose. A homology search in the genome of identified three WxL proteins with conserved counterparts of these three aromatic residues, and they were also found to be able to bind cellulose and xylan. The findings suggested a role of the cell-surface WxL and S-layer proteins in assisting the cellular adhesion of to plant cell wall polysaccharides.
木聚糖酶从膳食纤维木聚糖中释放木二糖寡糖，从而刺激肠道细菌乳杆菌的生长。许多乳杆菌附着在膳食纤维上，这可能有助于木二糖寡糖的吸收，并帮助它们在肠道中获得竞争力，但潜在的机制仍不清楚。在此，我们从富含培养物的转录本中报告，在补充木聚糖酶的小麦阿拉伯木聚糖中，鉴定出编码四个推定的细胞表面 WxL 蛋白（Lb630、Lb631、Lb632 和 Lb635）和一个 S-层蛋白（Lb1325）的基因，它们具有纤维素或木聚糖结合能力。重复出现的 WxL 蛋白由一个基因簇编码，其中选择 Lb630 进行进一步的突变研究。分析显示三个芳香族残基（F30、W61 和 W156）可能参与该蛋白与纤维素的相互作用。在基因组中的同源搜索确定了三个具有这些三个芳香族残基保守对应物的 WxL 蛋白，它们也被发现能够结合纤维素和木聚糖。这些发现表明细胞表面 WxL 和 S-层蛋白在协助附着在植物细胞壁多糖上的细胞黏附中发挥作用。
