4.4 Article

Structure of maize BZR1-type β-amylase BAM8 provides new insights into its noncatalytic adaptation

Journal

JOURNAL OF STRUCTURAL BIOLOGY
Volume 214, Issue 3, Pages -

Publisher

ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jsb.2022.107885

Keywords

beta-Amylase; BAM; Enzyme; BES1/BZR1; Noncatalytic; Crystal structure; Starch hydrolysis

Funding

  1. NSF -CAREER [2047396]
  2. NSF-EAGER [2028283]
  3. U.S. DOE Office of Science User Facility [DE-AC02-05CH11231]
  4. ALS- ENABLE program - National Institutes of Health, National Institute of General Medical Sciences [P30 GM124169-01]
  5. China Scholarship Council [CSC201906910056]
  6. Direct For Biological Sciences [2047396, 2028283] Funding Source: National Science Foundation
  7. Div Of Molecular and Cellular Bioscience [2028283, 2047396] Funding Source: National Science Foundation

Ask authors/readers for more resources

Plant beta-amylase proteins play crucial roles in plant growth, development, stress response, and hormone regulation. This study reveals the noncatalytic adaptation of BZR1-type beta-amylases and provides insights into their regulatory functions as putative metabolic sensors in plants.
Plant beta-amylase (BAM) proteins play an essential role in growth, development, stress response, and hormone regulation. Despite their typical (beta/alpha)(8) barrel structure as active catalysts in starch breakdown, catalytically inactive BAMs are implicated in diverse yet elusive functions in plants. The noncatalytic BAM7/8 contain N-terminal BZR1 domains and were shown to be involved in the regulation of brassinosteroid signaling and possibly serve as sensors of yet an uncharacterized metabolic signal. While the structures of several catalytically active BAMs have been reported, structural characterization of the catalytically inactive BZR1-type BAMs remain unknown. Here, we determine the crystal structure of beta-amylase domain of Zea mays BAM8/BES1/BZR1-5 and provide comprehensive insights into its noncatalytic adaptation. Using structural-guided comparison combined with biochemical analysis and molecular dynamics simulations, we revealed conformational changes in multiple distinct highly conserved regions resulting in rearrangement of the binding pocket. Altogether, this study adds a new layer of understanding to starch breakdown mechanism and elucidates the acquired adjustments of noncatalytic BZR1-type BAMs as putative regulatory domains and/or metabolic sensors in plants.

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