2IP2

Structure of the Pyocyanin Biosynthetic Protein PhzM

Summary for 2IP2

• Entry DOI: 10.2210/pdb2ip2/pdb
• Descriptor: Probable phenazine-specific methyltransferase (2 entities in total)
• Functional Keywords: methyltransferase, phenazine, pyocyanin, phenazine-1-carboxylic acid, phzm, transferase
• Biological source: Pseudomonas aeruginosa
• Total number of polymer chains: 2
• Total formula weight: 72794.81

Authors

Ladner, J.E.,Parsons, J.F.,Robinson, H.,Shi, K. (deposition date: 2006-10-11, release date: 2006-10-24, Last modification date: 2024-02-21)

Primary citation

Parsons, J.F.,Greenhagen, B.T.,Shi, K.,Calabrese, K.,Robinson, H.,Ladner, J.E.
Structural and functional analysis of the pyocyanin biosynthetic protein PhzM from Pseudomonas aeruginosa.
Biochemistry, 46:1821-1828, 2007

PubMed Abstract: 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.

PubMed: 17253782
DOI: 10.1021/bi6024403

Experimental method

X-RAY DIFFRACTION (1.8 Å)