title: NMR Study Reveals the Receiver Domain of Arabidopsis ETHYLENE RESPONSE1 Ethylene Receptor as an Atypical Type Response Regulator.
abstract: The gaseous plant hormone ethylene, recognized by plant ethylene receptors, plays a pivotal role in various aspects of plant growth and development. ETHYLENE RESPONSE1 (ETR1) is an ethylene receptor isolated from Arabidopsis and has a structure characteristic of prokaryotic two-component histidine kinase (HK) and receiver domain (RD), where the RD structurally resembles bacteria response regulators (RRs). The ETR1 HK domain has autophosphorylation activity, and little is known if the HK can transfer the phosphoryl group to the RD for receptor signaling. Unveiling the correlation of the receptor structure and phosphorylation status would advance the studies towards the underlying mechanisms of ETR1 receptor signaling. In this study, using the nuclear magnetic resonance technique, our data suggested that the ETR1-RD is monomeric in solution and the rigid structure of the RD prevents the conserved aspartate residue phosphorylation. Comparing the backbone dynamics with other RRs, we propose that backbone flexibility is critical to the RR phosphorylation. Besides the limited flexibility, ETR1-RD has a unique γ loop conformation of opposite orientation, which makes ETR1-RD unfavorable for phosphorylation. These two features explain why ETR1-RD cannot be phosphorylated and is classified as an atypical type RR. As a control, phosphorylation of the ETR1-RD was also impaired when the sequence was swapped to the fragment of the bacterial typical type RR, CheY. Here, we suggest a molecule insight that the ETR1-RD already exists as an active formation and executes its function through binding with the downstream factors without phosphorylation.
authors.affiliation: Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan.|Instrumentation Center, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Yi-Lin
authors.initials: YL
authors.lastname: Hung
authors.affiliation: Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Ingjye
authors.initials: I
authors.lastname: Jiang
authors.affiliation: Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Yi-Zong
authors.initials: YZ
authors.lastname: Lee
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Chi-Kuang
authors.initials: CK
authors.lastname: Wen
authors.affiliation: Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan.|Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Shih-Che
authors.initials: SC
authors.lastname: Sue
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D005030:Ethylenes / Q000378:metabolism* / Q000494:pharmacology; D019906:Nuclear Magnetic Resonance, Biomolecular; D010766:Phosphorylation; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D011494:Protein Kinases / Q000378:metabolism; D017433:Protein Structure, Secondary; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D029681:Arabidopsis Proteins; C494590:ETR1 protein, Arabidopsis; D005030:Ethylenes; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C083750:ethylene receptors, plant; C036216:ethylene; D011494:Protein Kinases