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Recceptor Allosteric Activation by the Plant Peptide Hormone Phytosulfokine
Wang Jizong1#, Li Hongju2#, Han Zhifu1, Zhang Heqiao1, Lin Guangzhong1, Chang Junbiao3, Yang Weicai2*, Chai Jijie1*
1Ministry of Education Key Laboratory of Protein Science, Center for Structural Biology, School of Life Sciences,Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing 100084, China;
2State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;
3Department of Chemistry, Zhengzhou University, Zhengzhou 450001, China
2State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;
3Department of Chemistry, Zhengzhou University, Zhengzhou 450001, China
Abstract: Phytosulfokine (PSK) is a kind of typical plant peptide signals， but has conserved five-amino acids sequence and two tyrosine sulfation modification in different species， playing a ubiquitous role in plant growth and development. PSK is perceived by its receptor PSKR， a leucine-rich repeat receptor kinase (LRR-RK).But the mechanism underlying recognition and activation remain elusive. Here we provide structural evidence that PSK mainly binds the island domainand the inner surface LRRs of PSKR， and PSK binding renders the island domain well structured by inducing violently conformational change. The two sulfate moieties of PSK directly interact with PSKR， sensitizing PSKR recognition of PSK. Supported by several lines of evidence， we verify that PSK binding induces PSKR heterodimerization with somatic embrogenesis receptor like kinases (SERKs). Our ternary activation complex structure reveals that PSK is not involved in PSKR-SERK interaction but stabilizes PSKR island domain for recruitment of a SERK， which differs to the classic “molecular glue” mechanism. Our data reveal the structural basis for PSKR recognition of PSK and an unprecedented mechanism of ligand-induced RK heterodimerization.
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