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Journal of Bacteriology, July 2007, p. 4739-4748, Vol. 189, No. 13
0021-9193/07/$08.00+0     doi:10.1128/JB.01889-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Molecular Characterization and Subcellular Localization of Macrophage Infectivity Potentiator, a Chlamydia trachomatis Lipoprotein{triangledown}

Laurence Neff,1,2 Sawsan Daher,3 Patrick Muzzin,4 Ursula Spenato,1 Fazil Gülaçar,3 Cem Gabay,1,2 and Sylvette Bas1*

Division of Rheumatology, Department of Internal Medicine, Geneva University Hospital,1 Department of Pathology and Immunology,2 Department of Cell Physiology and Metabolism, Geneva Medical School,4 Laboratory of Mass Spectrometry, University of Geneva, Geneva, Switzerland3

Received 14 December 2006/ Accepted 13 April 2007

Macrophage infectivity potentiator (MIP) was originally reported to be a chlamydial lipoprotein from experiments showing incorporation of radiolabeled palmitic acid into native and recombinant MIP; inhibition of posttranslational processing of recombinant MIP by globomycin, known to inhibit signal peptidase II; and solubility of native MIP in Triton X-114. However, the detailed structural characterization of the lipid moiety on MIP has never been fully elucidated. In this study, bioinformatics and mass spectrometry analysis, as well as radiolabeling and immunochemical experiments, were conducted to further characterize MIP structure and subcellular localization. In silico analysis showed that the amino acid sequence of MIP is conserved across chlamydial species. A potential signal sequence with a contained lipobox was identified, and a recombinant C20A variant was prepared by replacing the probable lipobox cysteine with an alanine. Both incorporation of U-14C-esterified glycerol and [U-14C]palmitic acid and posttranslational processing that was inhibitable by globomycin were observed for recombinant wild-type MIP but not for the recombinant C20A MIP variant. The fatty acid contents of native and recombinant MIP were analyzed by gas chromatography-mass spectrometry, and the presence of amide-linked fatty acids in recombinant MIP was investigated by alkaline methanolysis. These results demonstrated a lipid modification in MIP similar to that of other prokaryotic lipoproteins. In addition, MIP was detected in an outer membrane preparation of Chlamydia trachomatis elementary bodies and was shown to be present at the surfaces of elementary bodies by surface biotinylation and surface immunoprecipitation experiments.

* Corresponding author. Mailing address: Division of Rheumatology, Department of Internal Medicine, University Hospital, 1211 Geneva 14, Switzerland. Phone: (00 41 22) 3823680. Fax: (00 41 22) 3823535. E-mail: sylvette.bas{at}hcuge.ch

{triangledown} Published ahead of print on 20 April 2007.

Journal of Bacteriology, July 2007, p. 4739-4748, Vol. 189, No. 13
0021-9193/07/$08.00+0     doi:10.1128/JB.01889-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Lewenza, S., Mhlanga, M. M., Pugsley, A. P. (2008). Novel Inner Membrane Retention Signals in Pseudomonas aeruginosa Lipoproteins. J. Bacteriol. 190: 6119-6125 [Abstract] [Full Text]  
  • Bas, S., Neff, L., Vuillet, M., Spenato, U., Seya, T., Matsumoto, M., Gabay, C. (2008). The Proinflammatory Cytokine Response to Chlamydia trachomatis Elementary Bodies in Human Macrophages Is Partly Mediated by a Lipoprotein, the Macrophage Infectivity Potentiator, through TLR2/TLR1/TLR6 and CD14. J. Immunol. 180: 1158-1168 [Abstract] [Full Text]  


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