2ip2

Publication Abstract from PubMed

Pyocyanin is a biologically active phenazine produced by the human pathogen Pseudomonas aeruginosa. It is thought to endow P. aeruginosa with a competitive growth advantage in colonized tissue and is also thought to be a virulence factor in diseases such as cystic fibrosis and AIDS where patients are commonly infected by pathogenic Pseudomonads due to their immunocompromised state. Pyocyanin is also a chemically interesting compound due to its unusual oxidation-reduction activity. Phenazine-1-carboxylic acid, the precursor to the bioactive phenazines, is synthesized from chorismic acid by enzymes encoded in a seven-gene cistron in P. aeruginosa and in other Pseudomonads. Phenzine-1-carboxylic acid is believed to be converted to pyocyanin by the sequential actions of the putative S-adenosylmethionine-dependent N-methyltransferase PhzM and the putative flavin-dependent hydroxylase PhzS. Here we report the 1.8 A crystal structure of PhzM determined by single anomalous dispersion. Unlike many methyltransferases, PhzM is a dimer in solution. The 36 kDa PhzM polypeptide folds into three domains. The C-terminal domain exhibits the alpha/beta-hydrolase fold typical of small molecule methyltransferases. Two smaller N-terminal domains form much of the dimer interface. Structural alignments with known methyltransferases show that PhzM is most similar to the plant O-methyltransferases that are characterized by an unusual intertwined dimer interface. The structure of PhzM contains no ligands, and the active site is open and solvent-exposed when compared to structures of similar enzymes. In vitro experiments using purified PhzM alone demonstrate that it has little or no ability to methylate phenzine-1-carboxylic acid. However, when the putative hydroxylase PhzS is included, pyocyanin is readily produced. This observation suggests that a mechanism has evolved in P. aeruginosa that ensures efficient production of pyocyanin via the prevention of the formation and release of an unstable and potentially deleterious intermediate.

Structural and functional analysis of the pyocyanin biosynthetic protein PhzM from Pseudomonas aeruginosa.,Parsons JF, Greenhagen BT, Shi K, Calabrese K, Robinson H, Ladner JE Biochemistry. 2007 Feb 20;46(7):1821-8. Epub 2007 Jan 25. PMID:17253782^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.