Discovery and characterization of a marine bacterial SAM-dependent chlorinase.
Halogen atom incorporation into a scaffold of bioactive compounds often amplifies biological activity, as is the case for the anticancer agent salinosporamide A (1), a chlorinated natural product from the marine bacterium Salinispora tropica. Significant effort in understanding enzymatic chlorination shows that oxidative routes predominate to form reactive electrophilic or radical chlorine species. Here we report the genetic, biochemical and structural characterization of the chlorinase SalL, which halogenates S-adenosyl-L-methionine (2) with chloride to generate 5'-chloro-5'-deoxyadenosine (3) and L-methionine (4) in a rarely observed nucleophilic substitution strategy analogous to that of Streptomyces cattleya fluorinase. Further metabolic tailoring produces a halogenated polyketide synthase substrate specific for salinosporamide A biosynthesis. SalL also accepts bromide and iodide as substrates, but not fluoride. High-resolution crystal structures of SalL and active site mutants complexed with substrates and products support the S(N)2 nucleophilic substitution mechanism and further illuminate halide specificity in this newly discovered halogenase family.
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA. bsmoore@ucsd.edu
Alessandra S
AS
Eustáquio
Florence
F
Pojer
Joseph P
JP
Noel
Bradley S
BS
Moore
D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D018360:Crystallography, X-Ray; D005798:Genes, Bacterial; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry; D007783:Lactones / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008848:Micromonosporaceae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D011758:Pyrroles / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
D001426:Bacterial Proteins; D006843:Hydrocarbons, Chlorinated; D007783:Lactones; D011758:Pyrroles; C475865:marizomib; D012436:S-Adenosylmethionine