Cloning and Characterization of the Biosynthetic Gene Cluster for Tomaymycin, an SJG-136 Monomeric Analog

Abstract

Tomaymycin produced by Streptomyces achromogenes is a naturally produced pyrrolobenzodiazepine (PBD). The biosynthetic gene cluster for tomaymycin was identified and sequenced. The gene cluster analysis reveals a novel biosynthetic pathway for the anthranilate moiety of PBDs. Gene replacement and chemical complementation studies were used to confirm the proposed biosynthetic pathway.

Enterotoxicity of a nonribosomal peptide causes antibiotic-associated colitis

“…The K. oxytoca PAI genes show >50% amino acid sequence similarity to PBD synthesis genes from soil bacteria belonging to Actinomycetales, Streptomyces and Streptosporangium (Fig. S2B), which produce low-molecular-weight effector molecules with potent cytostatic activities (Fig.1E) (33)(34)(35). A capacity for production of other metabolites or virulence factors is not apparent within the PAI genes (Table S1).…”

Physiology, Biochemistry, and Applications of F420- and Fo-Dependent Redox Reactions

“…However, comparative genome analysis indicates that there are numerous other F 420 -dependent LLHTs in actinomycetes, the majority probably serving as reductases (37). These have been implicated in a variety of roles, ranging from pyrrolobenzodiazepene antibiotic synthesis in streptomycetes (50,393,394,429) to cell wall metabolism in mycobacteria (37) and exogenous substrate mobilization by rhodococci (155). A bioinformatics analysis predicted that there are some 45 F 420 -binding LLHTs in M. smegmatis and 17 in M. tuberculosis, though this has yet to be validated experimentally (37).…”

“…The nitrogen atom in position 5 is required for an unpaired electron to efficiently delocalize through the isoalloxazine ring; indeed, radicals of pyrazine groups (of flavins) are much lower energy than those of pyridine groups (of 5-deazaflavins) (7,43). Reflecting this reactivity, F 420 -dependent enzymes mediate diverse hydride transfer reactions that transform CϭC and C §C bonds (28,29,47,48), alcohol and imine groups (49,50), and certain inorganic compounds (51,52). Furthermore, due to the substitution, 5-deazaflavins do not readily undergo single-electron reactions.…”

“…However, biochemical studies have yet to definitively identify which enzymes are responsible for these reactions. The strongest candidates are the putative F 420 H 2 -dependent luciferase-like hydride transferases (LLHTs) encoded in the sequenced antibiotic synthesis gene clusters (50,391,(393)(394)(395) of each of these organisms. Because all research thus far has focused on the roles of F 420 in the secondary metabolism of streptomycetes, little is known about the roles of this cofactor in central metabolism of this genus; it is likely that streptomycetes use F 420 to support some important metabolic pathways, as they carry genes that encode homologs of mycobacterial enzymes such as the F 420 H 2 -dependent biliverdin reductase (30).…”

“…F 420 -dependent processes already provide essential steps in some industrial processes, for example in the synthesis of some of the oldest-known antibiotic classes (29,381), and there is considerable potential to expand the role of F 420 -dependent enzymes as catalysts for synthetic chemistry. F 420 H 2 -dependent reductases of the FDOR and LLHT superfamilies can catalyze the stereospecific reduction of enones (28,55,291,409) and imines (50,388,393) in diverse heterocycles. The broad substrate range of these enzymes may be particularly useful for catalyzing hydride addition to nonnatural compounds in a potentially stereospecific manner (479,480).…”