Related Experiment Videos
Ppm1, a novel polyprenol monophosphomannose synthase from Mycobacterium tuberculosis
Sudagar S Gurcha1, Alain R Baulard, Laurent Kremer
1Department of Microbiology and Immunology, The Medical School, The University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, UK.
Abstract:
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 lipoarabinomanan, 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.
Insights
Researchers identified and characterized the PPM synthase (Mt-Ppm1) in Mycobacterium tuberculosis, crucial for lipoarabinomanan biosynthesis. This enzyme offers a potential target for developing new tuberculosis inhibitors.
Area of Science:
- Microbiology
- Biochemistry
- Glycobiology
Background:
- Dolichol monophosphomannose (DPM) is vital for eukaryotic glycosylation.
- Polyprenol monophosphomannose (PPM) is essential for lipomannan and lipoarabinomanan biosynthesis in mycobacteria.
Purpose of the Study:
- To identify and characterize the PPM synthase in Mycobacterium tuberculosis.
- To investigate the enzymatic activity and domain structure of Mt-Ppm1.
Main Methods:
- Sequence homology to DPM synthases for identification.
- Overexpression of Mt-Ppm1 domains in mycobacteria.
- In vitro enzymatic assays using GDP-mannose and lipid monophosphate acceptors.
Main Results:
- Mt-Ppm1 exhibits a two-domain architecture; the second domain is sufficient for PPM synthesis.
- Overexpression of domain 1 also enhances PPM synthesis.
- Mt-Ppm1 transfers mannose to diverse lipid monophosphate acceptors.
- Related proteins homologous to Mt-Ppm1 domains exist in other mycobacteria.
Conclusions:
- PPM synthase is a key enzyme in lipoarabinomannan biosynthesis.
- Mt-Ppm1 is a potential target for gene disruption in immunological studies.
- PPM synthase represents a promising target for developing inhibitors against M. tuberculosis.