Invited Speaker Australian Society for Microbiology Annual Scientific Meeting 2021

Zinc-binding to the cytoplasmic PAS domain regulates the essential WalK histidine kinase of Staphylococcus aureus (#21)

Ian R Monk 1 , Nausad Shaikh 2 , Stephanie L Begg 1 , Mike Gajdiss 3 , Liam K. R. Sharkey 1 , Jean Y. H. Lee 1 , Sacha J Pidot 1 , Torsten Seemann 1 4 , Michael Kuiper 5 , Brit Winnen 2 , Rikki Hvorup 2 , Brett M Collins 2 , Gabriele Bierbaum 3 , Saumya R Udagedara 6 , Jacqueline R Morey 7 , Neha Pulyani 6 , Benjamin P Howden 1 , Megan J Maher 6 , Christopher A McDevitt 1 7 , Glenn F King 2 , Timothy P Stinear 1
  1. Department of Microbiology and Immunology, University of Melbourne, Melbourne, VIC, Australia
  2. Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland, Australia
  3. University Clinics of Bonn, Institute of Medical Microbiology, Immunology and Parasitology, Bonn, Germany
  4. Melbourne Bioformatics, University of Melbourne, Melbourne, VIC, Australia
  5. CSIRO Data61, Canberra, ACT, Australia
  6. Department of Biochemistry and Genetics, Le Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
  7. Department of Molecular and Biomedical Sciences, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia

WalKR is the only essential two-component signalling system (out of 16 pairs) in the human pathogen Staphylococcus aureus. WalKR regulates peptidoglycan synthesis, but this function alone does not explain its essentiality. Here, to further understand WalKR function, we investigate a suppressor mutant that arose when WalKR activity was impaired; a histidine to tyrosine substitution (H271Y) in the cytoplasmic Per-Arnt-Sim (PASCYTO) domain of the histidine kinase WalK. Introducing the WalKH271Y mutation into wild-type S. aureus activates the WalKR regulon. Structural analyses of the WalK PASCYTO domain reveal a metal-binding site, in which a zinc ion (Zn2+) is tetrahedrally-coordinated by four amino acids including H271. The WalKH271Y mutation abrogates metal binding, increasing WalK kinase activity and WalR phosphorylation in S. aureus. Thus, Zn2+-binding tempers the activation WalKR. Promoter-reporter experiments using S. aureus confirm Zn2+ sensing by this system. Identification of a metal ligand recognized by the WalKR system broadens our understanding and complexity of this critical S. aureus regulon.