Poster Presentation The 43rd Lorne Conference on Protein Structure and Function 2018

Revealing allosteric mechanisms of KLK4 inhibition through structural and dynamical characterisation (#224)

Blake T Riley 1 , Olga Ilyichova 2 , Itamar Kass 3 , Mauricio GS Costa 4 , David E Hoke 1 , Ashley M Buckle 1
  1. Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia
  2. Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
  3. Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia
  4. Scientific Computing Program (PROCC), Oswaldo Cruz Foundation (FIOCRUZ), Rio de Janeiro, RJ, Brazil

Kallikreins (KLKs) are a family of serine proteases important in development and normal physiology, and many have similar substrate specificities at P1 in the active site. Kallikrein-4 (KLK4) is predominantly involved in normal prostatic physiology, but has also been implicated in development and metastasis of some cancers. Determining how the activity of KLK4 is regulated is critical to developing selective inhibitors, and hence potential cancer therapeutics.

X-ray crystal structures of both apo-KLK4, and KLK4 in complex with an inhibitory, allosteric nickel (Ni) were determined. Additionally, these structures were subjected to molecular dynamics (MD) simulations to identify motions and conformations which differed between the structures.

In the Ni-KLK4 structure, an alternate conformation of the Asn192-Gly193 peptide bond in the oxyanion hole is observed, suggesting nickel inhibits KLK4 through destabilization of the oxyanion hole. An unstructured 70-80 loop region adjacent to the inhibitory metal binding site was also observed in the Ni-KLK4 structure. MD simulations show that metal binding induces differential motions that are transmitted to the active site. Our results provide an insight into indirect mechanisms of inhibition for KLK4, and a framework in which to explore pathways of allosteric inhibition that are applicable to the serine protease superfamily.