Junyu Xiao Ph. D and Professor
Group of protein structure and function
Assistant Professor, Peking University
1.Novel Secretory Pathway Kinases
2.Structure Biology of Macromolecular Machineries
1. Decipher the catalytic and substrate recognition mechanism of POMK
Protein O-mannose kinase (POMK, previously referred to as SgK196) is a carbohydrate kinase, and plays a critical role for the biosynthesis of functional alpha-dystroglycan. Despite compelling biochemical evidence in support of the kinase activity of POMK, its catalytic mechanism was puzzling, since it was long considered a pseudokinase. In a paper published in eLife, we have used a multidisciplinary approach to determine the architecture of the active site and the mechanisms underlying the catalytic and substrate-recognition activities of this unusual kinase. We show the crystal structure of POMK in complex with Mg2+ ions, ADP, aluminum fluoride, and the trisaccharide substrate. This structure provides a snapshot of the catalytic transition state of this glycan kinase, revealing an unprecedented kinase active site that is established by residues located in non-canonical positions and is stabilized by a disulfide bridge. Our results consolidate the catalytic function of POMK during the post-translational processing of alpha-DG, and facilitate a better understanding of the dystroglycanopathies and various physiological systems that depend on dystroglycan
2. Reveal an unprecedented ATP-binding mode in the pseudokinase Fam20A
Novel kinases specifically residing in the secretory pathway, exemplified by the family of sequence similarity 20 (Fam20) family, have been recently identified. Fam20C is the long-sought physiological Golgi casein kinase that phosphorylates many secreted proteins. Fam20A lacks an essential residue for catalysis and is therefore a pseudokinase. In a study published in eLife, we report the nucleotide-free and ATP-bound crystal structures of Fam20A. Fam20A displays an unusual disulfide pattern dictated by a pair of cysteine residues within the unique insertion region. Strikingly, ATP binds to Fam20A in an inverted orientation independent of cations. These results reinforce the conclusion that Fam20A is a pseudokinase in the secretory pathway and facilitate a deeper understanding of AI caused by Fam20A mutations.
3. Structural investigation of the inhibition mechanism of the Ethylene-forming enzyme by small molecule inhibitors
Ethylene is an important phytohormone that promotes the ripening of fruits and senescence of flowers thereby reducing their shelf lives. Specific ethylene biosynthesis inhibitors would help to decrease postharvest loss. Work from Dr. Hongwei Guo’s lab identify pyrazinamide (PZA), a clinical drug used to treat tuberculosis, as an inhibitor of ethylene biosynthesis in Arabidopsis thaliana, using a chemical genetics approach. PZA is converted to pyrazinecarboxylic acid (POA) in plant cells, suppressing the activity of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), the enzyme catalyzing the final step of ethylene formation. In collaboration with Dr. Guo’s group, we further determine the crystal structures of Arabidopsis ACO2 in complex with POA or 2-Picolinic Acid (2-PA), a POA-related compound. The structures reveal that POA/2-PA bind at the active site of ACO, preventing the enzyme from interacting with its natural substrates. Based on the structure information, we designed a series of ACO2 mutants and performed further biochemical experiments to validate the requirements of critical residues. Collectively, our studies demonstrate a different function of PZA in the control of plant ethylene biosynthesis, which holds potential applications in agriculture.
Liang K, Li NN, Wang X, Dai JY, Liu PL, Wang C, Chen XW, Gao N,Xiao JY. (2018) Cryo-EM structure of human mitochondrial trifunctional protein.Proc Natl Acad Sci US A., 115: 7039-7044.
Zhang H, Zhu QY, Cui JX, Wang YX, Chen MJ, Guo X, Tagliabracci VS, Dixon JE,Xiao JY. (2018) Structure and evolution of the Fam20 kinases.Nat Commun., 9: 1218.
Liu Y, Bhowmick T, Liu YQ, Gao XF, Mertens HDT, Svergun DI,Xiao JY, Zhang Y, Wang JH, Meijers R. (2018) Structural Basis for Draxin-Modulated Axon Guidance and Fasciculation by Netrin-1 through DCC.Neuron,97: 1261-1267.
Du S, Qu LJ,Xiao JY. (2018) Crystal structures of the extracellular domains of the CrRLK1L receptor-like kinases ANXUR1 and ANXUR2.Protein Sci., 27: 886-892.
Sun X, Li Y, He W, Ji C, Xia P, Wang Y, Du S, Li H, Raikhel N, Xiao JY, Guo HW (2017) Pyrazinamide and derivatives block ethylene biosynthesis by inhibiting ACC oxidase. Nature Communications, 8:15758.
Cui J, Zhu Q, Zhang H, Cianfrocco MA, Leschziner AE, Dixon JE, Xiao JY (2017) Structure of Fam20A reveals a pseudokinase featuring a unique disulfide pattern and inverted ATP-binding. eLife, 6: e23990.
Zhu Q, Venzke D, Walimbe AS, Anderson ME, Fu Q, Kinch LN, Wang W, Chen X, Grishin NV, Huang N, Yu L, Dixon JE, Campbell KP, Xiao JY (2016) Structure of protein O-mannose kinase reveals a unique active site architecture. eLife, 5: e22238.
Yu K, Yu Y, Tang X, Chen H, Xiao JY, Su XD. (2016) Transcriptome analyses of insect cells to facilitate baculovirus-insect expression. Protein Cell, 7: 373-382.
Tagliabracci VS*, Wen J, Xiao JY* (2016). Methods to Purify and Assay Secretory Pathway Kinases. Methods Mol Biol, 1496: 197-215.
Xiao JY, Tagliabracci VS, Wen J, Kim SA, Dixon JE. (2013) Crystal structure of the Golgi casein kinase. Proc. Natl. Acad. Sci. USA, 110: 10574-10579.
Jia Deng, Qinyu Zhu, Chuanping Gao, Hui Zhang, Kai Liang, Shuo Du, Yaxin Li, Zelin Duan, Zelin Duan, Chenggong Ji, Yuxin Wang, Tiantian Wei, Pulan Liu, Xiaoke Yang, Zhiying Zhang