Structure of a Bacterial ABC Transporter Involved in the Import of an Acidic Polysaccharide Alginate
Structure of a Bacterial ABC Transporter Involved in the Import of an Acidic Polysaccharide Alginate
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DOI：
10.1016/j.str.2015.06.021
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发表时间：
2015-09-01
期刊：
影响因子：
5.7
通讯作者：
Murata, Kousaku
中科院分区：
文献类型：
--
作者：
Maruyama, Yukie;Itoh, Takafumi;Murata, Kousaku
尽管藻酸盐转运体的分子和结构特征尚不清楚，但酸性藻酸盐多糖代表了微生物生产生物燃料的有前途的海洋生物质。在鞘氨单胞菌A1中，atp结合盒转运体AlgM1M2SS负责海藻酸盐穿过细胞质膜的进口。本文研究了AlgM1M2SS的底物输运特性和四元结构。多聚海藻酸盐或低聚海藻酸盐的加入增强了重组的AlgM1M2SS与一种质周溶质结合蛋白AlgQ1或AlgQ2偶联的atp酶活性。在存在AlgQ2、ATP和Mg2+的情况下，将外部荧光标记的低聚海藻酸盐特异性导入含有algm1m2ss的蛋白脂质体中。结合algq2的AlgM1M2SS晶体结构为内向构象。AlgQ2和AlgM1M2SS之间的相互作用诱导了溶剂可接近的海藻酸盐结合隧道状结构的形成。跨膜结构域内的易位路径包含适合导入酸性糖类的带电残基。
The acidic polysaccharide alginate represents a promising marine biomass for the microbial production of biofuels, although themolecular and structural characteristics of alginate transporters remain to be clarified. In Sphingomonas sp. A1, the ATP-binding cassette transporter AlgM1M2SS is responsible for the import of alginate across the cytoplasmic membrane. Here, we present the substrate-transport characteristics and quaternary structure of AlgM1M2SS. The addition of poly-or oligoalginate enhanced the ATPase activity of reconstituted AlgM1M2SS coupled with one of the periplasmic solute-binding proteins, AlgQ1 or AlgQ2. External fluorescence-labeled oligoalginates were specifically imported into AlgM1M2SS-containing proteoliposomes in the presence of AlgQ2, ATP, and Mg2+. The crystal structure of AlgQ2-bound AlgM1M2SS adopts an inward-facing conformation. The interaction between AlgQ2 and AlgM1M2SS induces the formation of an alginate-binding tunnel-like structure accessible to the solvent. The translocation route inside the transmembrane domains contains charged residues suitable for the import of acidic saccharides.