Laboratory of Basic and Applied Molecular Biotechnology, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto, 611-0011, Japan.
Laboratory of Applied Structural Biology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto, 611-0011, Japan.
Sci Rep. 2017 Apr 21;7(1):1069. doi: 10.1038/s41598-017-00917-y.
Glycosaminoglycans (GAGs), such as hyaluronan, chondroitin sulfate, and heparin, constitute mammalian extracellular matrices. The uronate and amino sugar residues in hyaluronan and chondroitin sulfate are linked by 1,3-glycoside bond, while heparin contains 1,4-glycoside bond. Some bacteria target GAGs as means of establishing colonization and/or infection, and bacterial degradation mechanisms of GAGs have been well characterized. However, little is known about the bacterial import of GAGs. Here, we show a GAG import system, comprised of a solute-binding protein (Smon0123)-dependent ATP-binding cassette (ABC) transporter, in the pathogenic Streptobacillus moniliformis. A genetic cluster responsible for depolymerization, degradation, and metabolism of GAGs as well as the ABC transporter system was found in the S. moniliformis genome. This bacterium degraded hyaluronan and chondroitin sulfate with an expression of the genetic cluster, while heparin repressed the bacterial growth. The purified recombinant Smon0123 exhibited an affinity with disaccharides generated from hyaluronan and chondroitin sulfate. X-ray crystallography indicated binding mode of Smon0123 to GAG disaccharides. The purified recombinant ABC transporter as a tetramer (Smon0121-Smon0122/Smon0120-Smon0120) reconstructed in liposomes enhanced its ATPase activity in the presence of Smon0123 and GAG disaccharides. This is the first report that has molecularly depicted a bacterial import system of both sulfated and non-sulfated GAGs.
糖胺聚糖（GAGs），如透明质酸、硫酸软骨素和肝素，构成了哺乳动物细胞外基质。透明质酸和硫酸软骨素中的糖醛酸和氨基糖残基通过 1,3-糖苷键连接，而肝素含有 1,4-糖苷键。一些细菌将 GAGs 作为建立定植和/或感染的手段，并且 GAGs 的细菌降解机制已经得到很好的描述。然而，关于细菌对 GAGs 的摄取知之甚少。在这里，我们展示了一种 GAG 摄取系统，由溶质结合蛋白（Smon0123）依赖性 ATP 结合盒（ABC）转运体组成，存在于致病性念珠状链杆菌中。在 S. moniliformis 基因组中发现了一个负责 GAG 解聚、降解和代谢以及 ABC 转运系统的基因簇。该细菌在表达该基因簇时降解透明质酸和硫酸软骨素，而肝素抑制细菌生长。纯化的重组 Smon0123 与透明质酸和硫酸软骨素衍生的二糖表现出亲和力。X 射线晶体学表明了 Smon0123 与 GAG 二糖的结合模式。作为四聚体（Smon0121-Smon0122/Smon0120-Smon0120）在脂质体中重建的纯化重组 ABC 转运体在存在 Smon0123 和 GAG 二糖的情况下增强了其 ATP 酶活性。这是首次报道了一种既能摄取硫酸化 GAGs 又能摄取非硫酸化 GAGs 的细菌摄取系统。
