Poster Presentation The 46th Lorne Conference on Protein Structure and Function 2021

Granulovirus PK-1 kinase activity relies on dimerisation via the N-lobe and αC helix (#419)

Chris R. Horne 1 2 , Michael R. Oliver 3 , Safal Shrestha 4 , Jeremy R. Keown 3 , Lung-Yu Liang 1 2 , Samuel N. Young 1 , Jarrod J. Sandow 1 2 , Andrew I. Webb 1 2 , David C. Goldstone 3 , Isabelle S. Lucet 1 2 , Natarajan Kannan 4 , Peter Metcalf 3 , James M. Murphy 1 2
  1. WEHI, Parkville, VIC, Australia
  2. Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
  3. School of Biological Sciences, University of Auckland, Auckland, New Zealand
  4. Institute of Bioinformatics, University of Georgia, Athens, GA, USA

The life cycle of Baculoviridae family insect viruses depends on the viral protein kinase, PK-1, to phosphorylate the regulatory DNA-binding protein, p6.9, to induce baculoviral genome release. Here, we report the crystal structure of Cydia pomenella granulovirus PK-1, which, owing to its likely ancestral origin among host cell AGC kinases, exhibits a eukaryotic protein kinase fold. PK-1 occurs as a rigid dimer, where an antiparallel arrangement of the αC helices at the dimer core stabilizes PK-1 in a closed, active conformation. Dimerisation is facilitated by C-lobe:C-lobe and N-lobe:N-lobe interactions between protomers, including the domain-swapping of an N-terminal helix that crowns a contiguous β-sheet formed by the two N-lobes. Molecular dynamics and biochemical studies illustrate PK-1 retains a dimeric conformation in solution, which is crucial for its catalytic activity. Our studies raise the prospect that “side-to-side” dimeric arrangements that lock kinase domains in a catalytically-active conformation could function more broadly as a regulatory mechanism among eukaryotic protein kinases.