RESUMEN
Dihydrofolate reductase (DHFR), a housekeeping enzyme in primary metabolism, has been extensively studied as a model of acid-base catalysis and a clinic drug target. Herein, we investigated the enzymology of a DHFR-like protein SacH in safracin (SAC) biosynthesis, which reductively inactivates hemiaminal pharmacophore-containing biosynthetic intermediates and antibiotics for self-resistance. Furthermore, based on the crystal structure of SacH-NADPH-SAC-A ternary complexes and mutagenesis, we proposed a catalytic mechanism that is distinct from the previously characterized short-chain dehydrogenases/reductases-mediated inactivation of hemiaminal pharmacophore. These findings expand the functions of DHFR family proteins, reveal that the common reaction can be catalyzed by distinct family of enzymes, and imply the possibility for the discovery of novel antibiotics with hemiaminal pharmacophore.
RESUMEN
A novel gene,located between dnrX and drrB in the genome of daunorubicin-producing strain Streptomyces coeruleorubidus SIPI-1482,was cloned and named as dauW.The full sequence of dauW was submitted to GenBank(Accession No.EF523565).Blast result indicated that it showed high homology with dnrW in GenBank.The exact function of dauW is as yet unknown despite the possibility that it might belong to a family of FAD-dependent oxidoreductases on the basis of conserved domain analysis.dauW was cloned into expression plasmids pET-28a(+)and pET-32a(+),respectively,and was successfully expressed in E.coli DE3 after induction with IPTG.The preliminary results of the expression of dauW suggested that it might be involved in the self resistance in Streptomyces coeruleorubidus due to the increased resistance to daunorubicin in the E.coli host.