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PDBsum entry 2ip2
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References listed in PDB file
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Key reference
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Title
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Structural and functional analysis of the pyocyanin biosynthetic protein phzm from pseudomonas aeruginosa.
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Authors
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J.F.Parsons,
B.T.Greenhagen,
K.Shi,
K.Calabrese,
H.Robinson,
J.E.Ladner.
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Ref.
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Biochemistry, 2007,
46,
1821-1828.
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PubMed id
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Abstract
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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.
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