Poster Presentation The 45th Lorne Conference on Protein Structure and Function 2020

Characterisation of Enterobacteriales effector proteins in complex with an innate immune DEAD Box RNA Helicase (#504)

Melissa N Sweeney 1 , Sarah C Atkinson 1 , Michelle D Audsley 1 , Natalie A Borg 1 2
  1. School of Biomedical Sciences, Monash University, Clayton, VIC, Australia
  2. School of Health and Biomedical Sciences, RMIT University, Bundoora, Victoria, Australia

Enterobacteriales is an order of gram-negative bacteria which encompasses the families Enterobacteriacea and Yersineacea. These families contain prominent pathogenic species which have a significant impact on human health, including the causative agent of the bubonic plague Yersinia pestis. These pathogenic bacteria encode effector proteins which are delivered into the cytoplasm of host cells via the Type III Secretion System. These effectors are essential for virulence and immune evasion strategies of these pathogens. One such protein is Yersinia Outer Protein M (YopM) which is required for full virulence of Yersinia strains, and is also found within the nucleus of infected cells (1, 2). The intranuclear roles and nuclear shuttling apparatus of YopM have not yet been widely characterised. However, dimeric Y. enterocolitica YopM has recently been shown to bind a host DEAD Box Helicase (DDX) (3). This DDX is commonly manipulated by viral proteins during infection (4-7). Y. enterocolitica is a novel example of a bacterial effector protein targeting DDX, and it may be that bacterial effector proteins likewise target this protein in their immune evasion and manipulation mechanisms.

Using various biophysical methods, we show that the Y. pestis YopM and structural homologues form novel complexes with this DDX. We also present evidence that these effectors have great flexibility and undergo conformational changes to bind this DDX as monomers via varied mechanisms. Our results add to our understanding of the mechanisms by which effector proteins, such as YopM, evade host immune responses. These findings will help to identify novel therapeutic targets for combating bacterial infections.

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