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Antimicrobial Agents and Chemotherapy, November 2005, p. 4576-4583, Vol. 49, No. 11
0066-4804/05/$08.00+0 doi:10.1128/AAC.49.11.4576-4583.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Industrial Biotechnology, SINTEF Materials and Chemistry, SINTEF, N-7034 Trondheim, Norway,1 Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway2
Received 3 June 2005/ Returned for modification 17 July 2005/ Accepted 21 August 2005
The genes nysH and nysG, encoding putative ABC-type transporter proteins, are located at the flank of the nystatin biosynthetic gene cluster in Streptomyces noursei ATCC 11455. To assess the possible roles of these genes in nystatin biosynthesis, they were inactivated by gene replacements leading to in-frame deletions. Metabolite profile analysis of the nysH and nysG deletion mutants revealed that both of them synthesized nystatin at a reduced level and produced considerable amounts of a putative nystatin analogue. Liquid chromatography-mass spectrometry and nuclear magnetic resonance structural analyses of the latter metabolite confirmed its identity as 10-deoxynystatin, a nystatin precursor lacking a hydroxyl group at C-10. Washing experiments demonstrated that both nystatin and 10-deoxynystatin are transported out of cells, suggesting the existence of an alternative efflux system(s) for the transport of nystatin-related metabolites. This notion was further corroborated in experiments with the ATPase inhibitor sodium o-vanadate, which affected the production of nystatin and 10-deoxynystatin in the wild-type strain and transporter mutants in a different manner. The data obtained in this study suggest that the efflux of nystatin-related polyene macrolides occurs through several transporters and that the NysH-NysG efflux system provides conditions favorable for C-10 hydroxylation.
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