Structural determinants of alternating (α1 → 4) and (α1 → 6) linkage specificity in reuteransucrase of Lactobacillus reuteri.
Structural determinants of alternating (α1 → 4) and (α1 → 6) linkage specificity in reuteransucrase of Lactobacillus reuteri.
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DOI：
10.1038/srep35261
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发表时间：
2016-10-17
影响因子：
4.6
通讯作者：
Dijkhuizen L
中科院分区：
文献类型：
--
作者：
Meng X;Pijning T;Dobruchowska JM;Yin H;Gerwig GJ;Dijkhuizen L
罗伊氏乳杆菌 121 的葡聚糖蔗糖酶 GTFA 产生具有大量交替 (α1 → 4) 和 (α1 → 6) 连接的 α-葡聚糖 (reuteran)。这种路德聚糖酶形成交替连接的机制仍不清楚。益生菌罗伊氏乳杆菌 ATCC 55730 的 GTFO 与罗伊氏乳杆菌 121 的 GTFA 具有高度序列相似性 (80%)；它还合成具有 (α1 → 4) 和 (α1 → 6) 键的 α-葡聚糖，但与 GTFA 相比，其比例明显不同。在本研究中，我们发现环977（970DGKGYKGA977）和螺旋α4（1083VSLKGA1088）中的残基是GTFO和GTFA之间连锁特异性差异的主要决定因素，因此对于GTFA中交替（α1 → 4）和（α1 → 6）连接的合成很重要。更远的受体底物结合位点（即+3）也参与交替连接合成的确定，如使用潘糖和麦芽三糖作为受体底物产生的寡糖的结构分析所示。我们的数据表明，受体底物结合位点（+1、+2、+3…）处的氨基酸残基共同形成了独特的理化微环境，决定了 GTFA 中交替的 (α1 → 4) 和 (α1 → 6) 连接合成。
The glucansucrase GTFA of Lactobacillus reuteri 121 produces an α-glucan (reuteran) with a large amount of alternating (α1 → 4) and (α1 → 6) linkages. The mechanism of alternating linkage formation by this reuteransucrase has remained unclear. GTFO of the probiotic bacterium Lactobacillus reuteri ATCC 55730 shows a high sequence similarity (80%) with GTFA of L. reuteri 121; it also synthesizes an α-glucan with (α1 → 4) and (α1 → 6) linkages, but with a clearly different ratio compared to GTFA. In the present study, we show that residues in loop977 (970DGKGYKGA977) and helix α4 (1083VSLKGA1088) are main determinants for the linkage specificity difference between GTFO and GTFA, and hence are important for the synthesis of alternating (α1 → 4) and (α1 → 6) linkages in GTFA. More remote acceptor substrate binding sites (i.e.+3) are also involved in the determination of alternating linkage synthesis, as shown by structural analysis of the oligosaccharides produced using panose and maltotriose as acceptor substrate. Our data show that the amino acid residues at acceptor substrate binding sites (+1, +2, +3…) together form a distinct physicochemical micro-environment that determines the alternating (α1 → 4) and (α1 → 6) linkages synthesis in GTFA.