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  MspA provides the main hydrophilic pathway through the cell wall of Mycobacterium smegmatis

Stahl, C., Kubetzko, S., Kaps, I., Seeber, S., Engelhardt, H., & Niederweis, M. (2001). MspA provides the main hydrophilic pathway through the cell wall of Mycobacterium smegmatis. Molecular Microbiology, 40(2), 451-464.

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Genre: Journal Article
Alternative Title : Mol. Microbiol

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Stahl, C., Author
Kubetzko, S., Author
Kaps, I., Author
Seeber, S., Author
Engelhardt, H.1, Author              
Niederweis, M., Author
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1External Organizations, ou_persistent22              

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Free keywords: Outer-membrane-protein; Beta-lactam antibiotics; Pore-forming properties; Gram-negative bacteria; Escherichia-coli; Permeability barrier; Mycolic acids; Porins; Gene; Tuberculosis.; Microbiology in Current Contents(R)/Life Sciences.
 Abstract: MspA is an extremely stable, oligomeric porin from Mycobacterium smegmatis that forms water-filled channels in vitro. Immunogold electron microscopy and an enzyme-linked immunosorbent assay demonstrated that MspA is localized in the cell wall. An mspA deletion mutant did not synthesize detectable amounts of mspA mRNA, as revealed by amplification using mspA-specific primers and reverse-transcribed RNA. Detergent extracts of the Delta mspA mutant exhibited a significantly lower porin activity in lipid bilayer experiments and contained about fourfold less porin than extracts of wild-type M. smegmatis. The chromosome of M. smegmatis encodes three proteins very similar to MspA, Sequence analysis of the purified porin revealed that mspB or mspC or both genes are expressed in the Delta mspA mutant. The properties of this porin, such as single channel conductance, extreme stability against denaturation, molecular mass and composition of 20 kDa subunits, are identical to those of MspA, Deletion of mspA reduced the cell wall permeability towards cephaloridine and glucose nine- and fourfold respectively. These results show that MspA is the main general diffusion pathway for hydrophilic molecules in M. smegmatis and was only partially replaced by fewer porins in the cell wall of the Delta mspA mutant. The minimal permeability coefficient of the Delta mspA mutant for glucose was 7.2 x 10(-8) cm s(-1), which is the lowest value reported so far for bacteria. This is the first experimental evidence that porins are the major determinants of the exceptionally low permeability of mycobacteria to hydrophilic molecules. [References: 44]

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 Dates: 2001
 Publication Status: Published in print
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 Identifiers: eDoc: 318338
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Title: Molecular Microbiology
  Alternative Title : Mol. Microbiol
Source Genre: Journal
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Pages: - Volume / Issue: 40 (2) Sequence Number: - Start / End Page: 451 - 464 Identifier: -