Griseoviridin

Mycobacterium aviumcomplex (MAC) is a serious disease mainly caused byM. aviumandM.intracellulare.Although the incidence of MAC infection is increasing worldwide, only a few agents are clinically used, and their therapeutic effects are limited. Therefore, new anti-MAC agents are needed. Approximately 6600 microbial samples were screened for new anti-mycobacterial agents that inhibit the growth of both M. avium and M. intracellulare, and two culture broths derived from marine actinomycete strains OPMA1245 and OPMA1730 had strong activity. Nosiheptide (1) was isolated from the culture broth of OPMA1245, and griseoviridin (2) and etamycin (viridogrisein) (3) were isolated from the culture broth of OPMA1730. They had potent anti-mycobacterial activity againstM.aviumandM.intracellularewith minimum inhibitory concentrations (MICs) between 0.024 and 1.56 μg/mL. In addition, a combination of 2 and 3 markedly enhanced the anti-mycobacterial activity against both M. avium and M. intracellulare. Furthermore, a combination 2 and 3 had a therapeutic effect comparable to that of ethambutol in a silkworm infection assay withM. smegmatis.

The antibiotic griseoviridin binds to the larger subunit of Escherichia coli ribosomes blocking the interaction between the 3' terminal end of peptidyl-tRNA and the donor site of the peptidyl transferase centre. Griseoviridin inhibits binding of chloramphenicol, thiamphenicol, lincomycin, erythromycin and streptogramin A to bacterial ribosomes. Moreover griseoviridin protects the ribosomal binding site of gougerotin from the drastic conformational changes taking place in the presence of ethanol. Griseoviridin is also able to interact with eukaryotic ribosomes as shown by its effects on model systems and on anisomycin, trichodermin and gougerotin binding studies. Nevertheless, griseoviridin affinity for the 80-S type ribosomes (yeast or human) is two orders of magnitude smaller than with E. coli ribosomes. The inhibitory spectrum and mode of action of griseoviridin on ribosomes is compared to that of antibiotics of the streptogramin A group and found to be essentially the same.

Griseoviridin (GV) is a broad-spectrum antibiotic with antibacterial and antifungal activity. In the GV biosynthetic pathway, SgvP catalyzes formation of the carbon-sulfur bond in GV. Herein, we report the recombinant expression and characterization of SgvP from Streptomyces griseoviridis NRRL2427. We also present the 2.6 Å crystal structure of SgvP, which is the first structure of a cytochrome P450 involved in carbon-sulfur bond formation in GV. Structural analysis indicates that Pro237 in the I-helix of SgvP may play a critical role in dioxygen binding and proton transfer during the catalytic cycle. Of the three channels we observed in SgvP, channel 3 may be essential for substrate ingress and egress from the active site, while channels 1 and 2 may be the solvent and water pathway, respectively.Database:Coordinate and structure factor were deposited in the Protein Data Bank database under the accession number 4MM0.