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Nat Plants. 2017 Dec;3(12):973-982. doi: 10.1038/s41477-017-0060-2. Epub 2017 Nov 27.

The crystal structure of Deg9 reveals a novel octameric-type HtrA protease.

Author information

1
Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
2
Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
3
The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel.
4
Research Institute of Molecular Pathology (IMP), Vienna, Austria.
5
Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China. Zhanglixin@ibcas.ac.cn.
6
College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China. Zhanglixin@ibcas.ac.cn.

Abstract

The high temperature requirement A (HtrA) proteases (also termed Deg proteases) play important roles in diverse organisms by regulating protein quality and quantity. One of the 16 Arabidopsis homologs, Deg9, is located in the nucleus where it modulates cytokinin- and light-mediated signalling via degrading the ARABIDOPSIS RESPONSE REGULATOR 4 (ARR4). To uncover the structural features underlying the proteolytic activity of Deg9, we determined its crystal structure. Unlike the well-established trimeric building block of HtrAs, Deg9 displays a novel octameric structure consisting of two tetrameric rings that have distinct conformations. Based on the structural architecture, we generated several mutant variants of Deg9, determined their structure and tested their proteolytic activity towards ARR4. The results of the structural and biochemical analyses allowed us to propose a model for a novel mechanism of substrate recognition and activity regulation of Deg9. In this model, protease activation of one tetramer is mediated by en-bloc reorientation of the protease domains to open an entrance for the substrate in the opposite (inactive) tetramer. This study provides the structural basis for understanding how the levels of nuclear signal components are regulated by a plant protease.

PMID:
29180814
DOI:
10.1038/s41477-017-0060-2
[Indexed for MEDLINE]

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