Crystal Structure and Catalytic Mechanism of CouO, a Versatile C-Methyltransferase from Streptomyces rishiriensis.
Friedel-Crafts alkylation of aromatic systems is a classic reaction in organic chemistry, for which regiospecific mono-alkylation, however, is generally difficult to achieve. In nature, methyltransferases catalyze the addition of methyl groups to a wide range of biomolecules thereby modulating the physico-chemical properties of these compounds. Specifically, S-adenosyl-L-methionine dependent C-methyltransferases possess a high potential to serve as biocatalysts in environmentally benign organic syntheses. Here, we report on the high resolution crystal structure of CouO, a C-methyltransferase from Streptomyces rishiriensis involved in the biosynthesis of the antibiotic coumermycin A1. Through molecular docking calculations, site-directed mutagenesis and the comparison with homologous enzymes we identified His120 and Arg121 as key functional residues for the enzymatic activity of this group of C-methyltransferases. The elucidation of the atomic structure and the insight into the catalytic mechanism provide the basis for the (semi)-rational engineering of the enzyme in order to increase the substrate scope as well as to facilitate the acceptance of SAM-analogues as alternative cofactors.
Institute of Molecular Biosciences, University of Graz, Graz, Austria.|ACIB, Austrian Centre of Industrial Biotechnology GmbH, Graz, Austria.
Tea
T
Pavkov-Keller
ACIB, Austrian Centre of Industrial Biotechnology GmbH, Graz, Austria.
Kerstin
K
Steiner
Institute of Molecular Biotechnology Graz University of Technology, Graz, Austria.|Institute of Organic Chemistry, Graz University of Technology, Graz, Austria.
Mario
M
Faber
ACIB, Austrian Centre of Industrial Biotechnology GmbH, Graz, Austria.|Institute of Molecular Biotechnology Graz University of Technology, Graz, Austria.
Martin
M
Tengg
ACIB, Austrian Centre of Industrial Biotechnology GmbH, Graz, Austria.|Institute of Molecular Biotechnology Graz University of Technology, Graz, Austria.
Helmut
H
Schwab
ACIB, Austrian Centre of Industrial Biotechnology GmbH, Graz, Austria.|Institute of Organic Chemistry, Graz University of Technology, Graz, Austria.
Mandana
M
Gruber-Khadjawi
Institute of Molecular Biosciences, University of Graz, Graz, Austria.|ACIB, Austrian Centre of Industrial Biotechnology GmbH, Graz, Austria.
Karl
http://orcid.org/0000-0002-3485-9740
K
Gruber
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008780:Methyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D011487:Protein Conformation; D012435:S-Adenosylhomocysteine / Q000737:chemistry / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology*
D001426:Bacterial Proteins; D012435:S-Adenosylhomocysteine; D008780:Methyltransferases