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

Crystal Structure of Mycobacterium Tuberculosis Protein Kinase G (#268)

David Ruiz Carrillo 1 , Yuanhao Zhao 1 , Kaiyuan Chen 1
  1. Xi'an Jiaotong Liverpool University, Suzhou, JIANGSU, China

Tuberculosis (TB) is an infectious disease still infringing a heavy burden on society (1). Microbial protein kinases have been proposed as target for new antimicrobial. Sequencing of the Mycobacterium tuberculosis (Mtb) genome (2) has shown the presence of an small microbial eukaryotic Ser/Thr like protein kinase family (3, 4). Among the members of this family protein kinase G (PknG) (5) stood out because infection mice models with a Mtb ∆PknG mutant resulted in prolonged mice survival and decreased parasite’s viability (6), making it an attractive target for drug development. We are expressing and purifying a construct of Mtb-PknG that was previously used for its structural characterization  (7) aiming at identifying new crystallographic forms of the protein. We report here a preliminary structure obtained after extensive crystallization trials leading to a hit that could be developed into a diffracting crystal rendering a new crystal structure at a resolution of 3.35 Angstroms (Illustration). Like shown previously (7),  two molecules still appear in the asymmetric unit however here the intermolecular interface rearranges in a new non-crystallographic dimer. The electron density allows unambiguously the identification of polypeptide chains and side chains. Model building was particularly challenged by positive electron densities that concerned main regions of the Rubredoxin domain, indicating the flexible nature of this domain. The new preliminary structure shows significant rearrangements of the N terminal domains and Kinase domain, while the Tetratricopeptide domain is less conformationally affected when compared to previous models (Illustration). Moreover, despite of the use of substrate analogues during the whole crystallogenesis process, the protein unexpectedly appeared in an apo-substrate form, a fact that may help in the description of the active site if aiming at the development of new inhibitory molecules when compared to previous structural works that as well focused on PknG (7,8)


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  9. Illustration: A. PknG structures superimposed. In blue and red are shown this work and PDB code 2pzi, respectively. B. Detail of the Rubredoxin and kinase domains are shown. Figure was prepared with Pymol and Image Magick.
  10. The plasmid used in this work was gift of Prof J Pieters from the Biozentrum - University of Basel (Switzerland)