Mechanistic insights into c-di-GMP–dependent control of the biofilm regulator FleQ from Pseudomonas aeruginosa

Bruno y Matsuyama (1) , Petya V. Krasteva (2, 3) , Claudine Baraquet (4) , Caroline S Harwood (4) , Holger Sondermann (3) , Marcos V a S Navarro (1)

1 IFSC-USP - Instituto de Física de São Carlos
2 Biologie Structurale de la Sécrétion Bactérienne
3 Cornell University [New York]
4 University of Washington [Seattle]

Bacterial biofilm formation during chronic infections confers increased fitness, antibiotic tolerance, and cytotoxicity. In many pathogens, the transition from a planktonic lifestyle to collaborative, sessile biofilms represents a regulated process orchestrated by the intracellular second-messenger c-di-GMP. A main effector for c-di-GMP signaling in the opportunistic pathogen Pseudomonas aeruginosa is the transcription regulator FleQ. FleQ is a bacterial enhancer-binding protein (bEBP) with a central AAA+ ATPase σ54-interaction domain, flanked by a C-terminal helix-turn-helix DNA-binding motif and a divergent N-terminal receiver domain. Together with a second ATPase, FleN, FleQ regulates the expression of flagellar and exopolysaccharide biosynthesis genes in response to cellular c-di-GMP. Here we report structural and functional data that reveal an unexpected mode of c-di-GMP recognition that is associated with major conformational rearrangements in FleQ. Crystal structures of FleQ’s AAA+ ATPase domain in its apo-state or bound to ADP or ATP-γ-S show conformations reminiscent of the activated ring-shaped assemblies of other bEBPs. As revealed by the structure of c-di-GMP–complexed FleQ, the second messenger interacts with the AAA+ ATPase domain at a site distinct from the ATP binding pocket. c-di-GMP interaction leads to active site obstruction, hexameric ring destabilization, and discrete quaternary structure transitions. Solution and cell-based studies confirm coupling of the ATPase active site and c-di-GMP binding, as well as the functional significance of crystallographic interprotomer interfaces. Taken together, our data offer unprecedented insight into conserved regulatory mechanisms of gene expression under direct c-di-GMP control via FleQ and FleQ-like bEBPs.

Mots clés: enhancer binding protein; flagella structure; gene expression; flagella; structure

Domaines: Sciences du Vivant [q-bio]

Bruno y Matsuyama, Petya V. Krasteva, Claudine Baraquet, Caroline S Harwood, Holger Sondermann, et al.. Mechanistic insights into c-di-GMP–dependent control of the biofilm regulator FleQ from Pseudomonas aeruginosa. Proceedings of the National Academy of Sciences of the United States of America, 2015, 113 (2), pp.E209 - E218. ⟨10.1073/pnas.1523148113⟩. ⟨hal-03115322⟩