Starch is a key energy‐storage molecule in plants that requires controlled synthesis and breakdown for effective plant growth. β‐Amylases (BAMs) hydrolyze starch into maltose to help to meet the metabolic needs of the plant. In the model plant Arabidopsis thaliana there are nine BAMs, which have apparently distinct functional and domain structures, although the functions of only a few of the BAMs are known and there are no 3D structures of BAMs from this organism. Recently, AtBAM2 was proposed to form a tetramer based on chromatography and activity assays of mutants; however, there was no direct observation of this tetramer. Here, small‐angle X‐ray scattering data were collected from AtBAM2 and its N‐terminal truncations to describe the structure and assembly of the tetramer. Comparison of the scattering of the AtBAM2 tetramer with data collected from sweet potato (Ipomoea batatas) BAM5, which is also reported to form a tetramer, showed there were differences in the overall assembly. Analysis of the N‐terminal truncations of AtBAM2 identified a loop sequence found only in BAM2 orthologs that appears to be critical for AtBAM2 tetramer assembly as well as for activity.

中文翻译：

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拟南芥 β-淀粉酶 2 的溶液结构和组装。

淀粉是植物中的一种关键的能量储存分子，需要受控的合成和分解才能保证植​​物的有效生长。β-淀粉酶 (BAM) 将淀粉水解成麦芽糖，有助于满足植物的代谢需求。在模型植物拟南芥中，有 9 个 BAM，它们具有明显不同的功能和域结构，尽管只有少数 BAM 的功能是已知的，并且没有来自该生物体的 BAM 的 3D 结构。最近，基于突变体的色谱和活性测定，AtBAM2被提议形成四聚体；然而，没有直接观察到该四聚体。在这里，从 AtBAM2 及其 N 末端截断收集小角 X 射线散射数据，以描述四聚体的结构和组装。AtBAM2 四聚体的散射与从甘薯 ( Ipomoea batatas ) BAM5（据报道也形成四聚体）收集的数据进行比较，表明整体组装存在差异。对 AtBAM2 N 端截短的分析发现了仅在 BAM2 直向同源物中发现的环序列，该序列似乎对于 AtBAM2 四聚体组装以及活性至关重要。