The zinc protease AmpDh2 is a virulence determinant of Pseudomonas aeruginosa, a problematic human pathogen. The mechanism of how the protease manifests virulence is not known, but it is known that it turns over the bacterial cell wall. A research conducted by the Instituto de Química-Física Rocasolano and the University of Notre Dame (Indiana, USA) provided insights into the mechanism of action of AmpDh2. The reaction of AmpDh2 with the cell wall was investigated and nine distinct turnover products were characterized by LC/MS/MS. The enzyme turns over both the crosslinked and non-crosslinked cell wall. Three high-resolution X-ray structures, of the apo enzyme and of two complexes with turnover products, were solved. The X-ray structures show how the dimeric protein interacts with the inner leaflet of the bacterial outer membrane and that the two monomers provide a more expansive surface for recognition of the cell wall. This binding surface can accommodate the three-dimensional solution structure of the crosslinked cell wall. We have disclosed in this report the nature of the reactions of AmpDh2 with the bacterial sacculus and have determined the structure of the protein, which reveals the importance of the dimeric nature in accommodating larger segments of the cell wall. The present study reveals at atomic detail the structural attributes of this important virulence factor of P. areruginosa in the reactions that it performs, which are at the roots of the manifestation of the virulence.

 Reference:

Siseth Martínez-Caballero, Mijoon Lee, Cecilia Artola-Recolons, César Carrasco-López, Dusan Hesek, Edward Spink, Elena Lastochkin, Weilie Zhang, Lance M. Hellman, Bill Boggess, Shahriar Mobashery* and Juan A. Hermoso*

Reaction products and the X-ray structure of AmpDh2, a virulence determinant of Pseudomonas aeruginosa.

Journal of the American Chemical Society (2013) 135, - (in press)  (doi:10.1021/ja405464b)