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Jianyong Li

Virginia Tech, USA

Title: A structure complex of a bacterial effort and an interacting protein: insights into the transfer of virulence effector by pathogenic bacteria

Biography

Biography: Jianyong Li

Abstract

Bacterial effectors are proteins secreted by pathogenic bacteria into host cells through a type 3 or 4 secretion system. These bacterial effectors may help the pathogens to invade host cells and/or suppress its immune system; thereby promoting their infection, survival and reproduction. Effector proteins are primarily responsible for the pathogenicity of a given bacterial pathogen; therefore, learning the specific mechanism but which their effectors enter into host cells may provide insights for disease prevention. Bacterial Type 3 secretion system (T3SS) has been extensively studied. It is a needle-like structure made by a number of structural proteins, which is responsible for transfer of protein effector to host cells. The needle tip is ~ 3 nm, which is smaller than the required dimension for most bacterial effectors.  Despite some better understanding of the T3SS structure, how their bacterial effectors gain entry to host cells remains speculative. Using a T3SS-dependant effector as a model from Xanthomonas oryzae (a bacterium causing serious disease to some essential plants), we determined the structures of an effector protein in complex with a chaperone-like protein. In the genome of Xanthomonas oryzae, the coding sequence of effector protein is adjacent to that coding the chaperone-like protein. Our structural analysis indicates that the effector-chaperon complex crystallized as tetramers (1.64 A resolution). The monomer of the protein effector contains a T4 polynucleotide kinase domain, while the monomer of the chaperon includes a novel kinase binding domain. Our data suggest that the chaperone protein interacts with the protein effector in a manner that helps to stabilize the protein effector and prevents the virulence effect of protein effort from harming the bacteria before being transferred to host cells. Currently, efforts are being made to understand the precise roles the chaperon protein plays during the transfer of protein effector to host cells. 

References:

  1. Han et al. (2017) Crystal structure of acetylcholinesterase subunits of the malaria vector Anopheles gambiae. Insect Science (https://www.ncbi.nlm.nih.gov/pubmed/28247978).
  2. Carlier PR, Bloomquist JR, Totrov M and Li J (2017) Discovery of species-selective and resistance-breaking anticholinesterase insecticide for the malaria mosquito. Current Medical Chemistry (https://www.ncbi.nlm.nih.gov/pubmed/28176636)
  3. Yang et al. (2016) Kynurenine aminotransferase 3/glutamine transaminase L/cysteine conjugate beta-lyase 2 is a major glutamine transaminase in the mouse kidney. Biochemistry and Biophysics Reports 8: 231-241. 
  4. Han Q et al. (2015) crystal structure of the complex between AvrRxo1-ORF1, a type III effector and its cognate chaperon, AvrRxo1-ORF2. Structure 23: 1900-1909 (http://www.sciencedirect.com/science/article/pii/S0969212615003251).
  5. Han Q, Robinson H, Ding H, Christensen BM and Li J (2012) Evolution of insect arylalkylamine N-acetyltransferases: structural evidence from the yellow fever mosquito, Aedes aegypti. Proceedings of the National Academy of Sciences 109: 11669-11674.