The BAM7 gene in Zea mays encodes a protein with similar structural and catalytic properties to Arabidopsis BAM2
The BAM7 gene in Zea mays encodes a protein with similar structural and catalytic properties to Arabidopsis BAM2
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DOI：
10.1107/s2059798322002169
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发表时间：
2022-05-01
影响因子：
2.2
通讯作者：
Berndsen, Christopher E.
中科院分区：
文献类型：
--
作者：
Ravenburg, Claire M.;Riney, McKayla B.;Berndsen, Christopher E.
淀粉在白天积累在绿色植物组织的质体中，为晚上的新陈代谢提供碳。淀粉水解由β-淀粉酶（BAM）家族的成员催化，该家族在拟南芥（At）中包括9个结构和功能不同的成员。这些酶之一，AtBAM 2，是一种质体定位的酶，它是独特的表征β-淀粉酶，因为它是四聚体，并表现出S形动力学。序列比对表明，BAM结构域的AtBAM 7，催化失活，核定位的转录因子与N-末端DNA结合结构域，和AtBAM 2是更密切相关的彼此比他们是任何其他AtBAM。由于BAM 2基因存在于更古老的谱系中，因此假设BAM 7基因是从BAM 2进化而来的。然而，对48种开花植物的基因组分析显示，12种植物似乎拥有BAM 7基因，但缺乏BAM 2基因。经过仔细检查，这些BAM 7蛋白与AtBAM 2的同一性百分比大于AtBAM 7，并且它们共享BAM 7蛋白通常缺乏的所有AtBAM 2功能残基。假设这些基因可能编码BAM 2样蛋白，尽管它们目前被注释为BAM 7样基因。为了检验这一假设，设计了玉米BAM 7的短形式（ZmBAM 7-S）的cDNA用于在大肠杆菌中表达。小角X射线散射数据表明，ZmBAM 7-S具有四聚体溶液结构，其与AtBAM 2的结构比与AtBAM 1的结构更相似。此外，部分纯化的ZmBAM 7-S是催化活性的并且表现出S形动力学。总之，这些数据表明，一些BAM 7基因可能编码功能性BAM 2。探索和理解β-淀粉酶基因结构可能会对目前的基因注释产生影响。
Starch accumulates in the plastids of green plant tissues during the day to provide carbon for metabolism at night. Starch hydrolysis is catalyzed by members of the beta-amylase (BAM) family, which in Arabidopsis thaliana (At) includes nine structurally and functionally diverse members. One of these enzymes, AtBAM2, is a plastid-localized enzyme that is unique among characterized beta-amylases since it is tetrameric and exhibits sigmoidal kinetics. Sequence alignments show that the BAM domains of AtBAM7, a catalytically inactive, nuclear-localized transcription factor with an N-terminal DNA-binding domain, and AtBAM2 are more closely related to each other than they are to any other AtBAM. Since the BAM2 gene is found in more ancient lineages, it was hypothesized that the BAM7 gene evolved from BAM2. However, analysis of the genomes of 48 flowering plants revealed 12 species that appear to possess a BAM7 gene but lack a BAM2 gene. Upon closer inspection, these BAM7 proteins have a greater percent identity to AtBAM2 than to AtBAM7, and they share all of the AtBAM2 functional residues that BAM7 proteins normally lack. It is hypothesized that these genes may encode BAM2-like proteins although they are currently annotated as BAM7-like genes. To test this hypothesis, a cDNA for the short form of corn BAM7 (ZmBAM7-S) was designed for expression in Escherichia coli. Small-angle X-ray scattering data indicate that ZmBAM7-S has a tetrameric solution structure that is more similar to that of AtBAM2 than to that of AtBAM1. In addition, partially purified ZmBAM7-S is catalytically active and exhibits sigmoidal kinetics. Together, these data suggest that some BAM7 genes may encode a functional BAM2. Exploring and understanding the beta-amylase gene structure could have an impact on the current annotation of genes.