Catalytic pocket of Pseudomonas aeruginosa phosphorylcholine phosphatase for Mg2+, Zn2+ and Cu2+.

OTERO, LH; BEASSONI, PR; LISA, AT; DOMENECH, CE

Rosario, Argentina

Congreso; XLII Reunión Anual, Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

PA5292 from P. aeruginosa PAO1 is the gene responsible for the synthesis of phosphorylcholine phosphatase (PChP). It belongs to the Mg2+ dependent family of phosphomutases and phosphatases containing motifs I, II and III. In PChP these motifs are the aminoacyl residues 31DMDNT35, 166SAA168 and K242/261GDTPDSD267, respectively. D33, D262 and D267 are involved in the binding pocket for Mg2+. Since Cu2+ and Zn2+ were more efficient activators than Mg2+ either from the native or the recombinant PChP, the aim of this work was to know the interaction of divalent cations from Cu and Zn in the catalytic pocket for Mg. The substitution of Asp by Glu or Ala in motif I abolished the enzyme activity. The substitution S167T or D267E resulted in enzymes better activated by Mg or Zn than for Cu. Changes in the catalytic efficiency were also observed in D262E and D267E. D262E decreases the affinity for Mg but conserves the same affinity by Cu than the WT enzyme. In D267E, Mg is more efficient than Cu and Zn+2 to activate PChP. These results indicated that the catalytic pocket for Mg is also involved for Cu and Zn and may be explained considering the 3D model, where it predicts a retraction of the carboxilic group of 5 Å in D262E or 2.4 Å in D267E. Since the ionic radius of these cations is similar (0.86-0.88 Å) it is possible that the coordination index is responsible for the described differences.