Enzymatic Generation of the Antimetabolite γ,γ-Dichloroaminobutyrate by NRPS and Mononuclear Iron Halogenase Action in a Streptomycete
Four adjacent open reading frames, cytC1–C4, were cloned from a cytotrienin-producing strain of a Streptomyces sp. by using primers derived from the conserved region of a gene encoding a nonheme iron halogenase, CmaB, in coronamic acid biosynthesis. CytC1–3 were active after expression in Escherichia coli, and CytC4 was active after expression in Pseudomonas putida. CytC1, a relatively promiscuous adenylation enzyme, installs the aminoacyl moieties on the phosphopantetheinyl arm of the holo carrier protein CytC2. CytC3 is a nonheme iron halogenase that will generate both γ-chloro- and γ,γ-dichloroaminobutyryl-S-CytC2 from aminobutyryl-S-CytC2. CytC4, a thioesterase, hydrolytically releases the dichloroaminobutyrate, a known streptomycete antibiotic. Thus, this short four-protein pathway is likely the biosynthetic source of this amino acid antimetabolite. This four-enzyme system analogously converts the proS-methyl group of valine to the dichloromethyl product regio- and stereospecifically.
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Masashi Ueki, Danica P. Galonić, Frédéric H. Vaillancourt, Sylvie Garneau-Tsodikova, Ellen Yeh, David A. Vosburg, Frank C. Schroeder, Hiroyuki Osada, Christopher T. Walsh, Enzymatic Generation of the Antimetabolite γ,γ-Dichloroaminobutyrate by NRPS and Mononuclear Iron Halogenase Action in a Streptomycete, Chemistry & Biology, Volume 13, Issue 11, November 2006, Pages 1183-1191, ISSN 1074-5521, http://dx.doi.org/10.1016/j.chembiol.2006.09.012. (http://www.sciencedirect.com/science/article/pii/S1074552106003450)