Dolichol monophosphomannose (DPM) is an ever-present donor of mannose (Man) in various eukaryotic glycosylation processes. Intriguingly, the related polyprenol monophosphomannose (PPM) is involved in the biosynthesis of lipomannan and lipoarabinomannan, key bacterial factors termed modulins that are found in mycobacteria. Based on similarities to known DPM synthases, we have identified and characterized the PPM synthase of Mycobacterium tuberculosis, now termed Mt-Ppm1. In the present study, we demonstrate that Mt-Ppm1 possesses an unusual two-domain architecture, by which the second domain is sufficient for PPM synthesis. However, when overexpressed separately in mycobacteria, domain 1 of Mt-Ppm1 appears to increase the synthesis of PPM. Interestingly, other mycobacteria such as M. smegmatis, M. avium and M. leprae produce two distinct proteins, which are similar to the two domains found in Mt-Ppm1. Using an in vitro assay, we also demonstrate that Mt-Ppm1 transfers Man from GDP-Man to a structurally diverse range of lipid monophosphate acceptors. The identification of the PPM synthase as a key enzyme in lipoarabinomannan biosynthesis now provides an attractive candidate for gene disruption to generate mutants for subsequent immunological studies. PPM synthase can also be exploited as a target for specific inhibitors of M. tuberculosis
lipoarabinomannan, Mannosyltransferase, GDP-mannose
NCBI PubMed ID: 11931640Publication DOI: 10.1042/BJ20020107Journal NLM ID: 2984726RPublisher: London, UK : Published by Portland Press on behalf of the Biochemical Society
Correspondence: g.besra@bham.ac.uk
Institutions: Department of Microbiology and Immunology, The Medical School, The University of Newcastle upon Tyne, Newcastle upon Tyne, UK, INSERM U447, Institut Pasteur de Lille, Lille, France, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital and Harvard Medical School, Boston, USA, Mass Spectroscopy Resource, Boston University School of Medicine, Boston, USA, Department of Microbiology, Colorado State University, Fort Collins, USA
Methods: DNA techniques, TLC, ESI-MS, radiolabeling, radioactivity measurement, extraction, cell growth, centrifugation
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