Novel structural and regulatory features of rhoptry secretory kinases in Toxoplasma gondii

Qiu, W., Wernimont, A., Tang, K., Taylor, S., Lunin, V., Schapira, M., Fentress, S., Hui, R. and Sibley, L.D. (2009) Novel structural and regulatory features of rhoptry secretory kinases in Toxoplasma gondii. EMBO Journal, 28(7), pp. 969-979. (doi: 10.1038/emboj.2009.24)

Abstract

Serine/threonine kinases secreted from rhoptry organelles constitute important virulence factors of Toxoplasma gondii. Rhoptry kinases are highly divergent and their structures and regulatory mechanism are hitherto unknown. Here, we report the X-ray crystal structures of two related pseudokinases named ROP2 and ROP8, which differ primarily in their substrate-binding site. ROP kinases contain a typical bilobate kinase fold and a novel N-terminal extension that both stabilizes the N-lobe and provides a unique means of regulation. Although ROP2 and ROP8 were catalytically inactive, they provided a template for homology modelling of the active kinase ROP18, a major virulence determinant of T. gondii. Autophosphorylation of key residues in the N-terminal extension resulted in ROP18 activation, which in turn phosphorylated ROP2 and ROP8. Mutagenesis and mass spectrometry experiments revealed that ROP18 was maximally activated when this phosphorylated N-terminus relieved autoinhibition resulting from extension of aliphatic side chains into the ATP-binding pocket. This novel means of regulation governs ROP kinases implicated in parasite virulence.

• Item Type: Articles
• Keywords: autophosphorylation; serine/threonine kinase; signaling; virulence factor
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Taylor, Dr Sonya
• Authors: Qiu, W., Wernimont, A., Tang, K., Taylor, S., Lunin, V., Schapira, M., Fentress, S., Hui, R., and Sibley, L.D.
• Subjects: Q Science > QR Microbiology > QR180 Immunology
• College/School: College of Medical Veterinary and Life Sciences; College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: EMBO Journal
• ISSN: 0261-4189
• ISSN (Online): 1460-2075
• Published Online: 05 February 2009