Mycobacterium smegmatis laminin-binding glycoprotein shares epitopes with Mycobacterium tuberculosis heparin-binding haemagglutinin.
Mycobacterium tuberculosis, the causative agent of tuberculosis, produces a heparin-binding haemagglutinin adhesin (HBHA), which is involved in its epithelial adherence. To ascertain whether HBHA is also present in fast-growing mycobacteria, Mycobacterium smegmatis was studied using anti-HBHA monoclonal antibodies (mAbs). A cross-reactive protein was detected by immunoblotting of M. smegmatis whole-cell lysates. However, the M. tuberculosis HBHA-encoding gene failed to hybridize with M. smegmatis chromosomal DNA in Southern blot analyses. The M. smegmatis protein recognized by the anti-HBHA mAbs was purified by heparin-Sepharose chromatography, and its amino-terminal sequence was found to be identical to that of the previously described histone-like protein, indicating that M. smegmatis does not produce HBHA. Biochemical analysis of the M. smegmatis histone-like protein shows that it is glycosylated like HBHA. Immunoelectron microscopy demonstrated that the M. smegmatis protein is present on the mycobacterial surface, a cellular localization inconsistent with a histone-like function, but compatible with an adhesin activity. In vitro protein interaction assays showed that this glycoprotein binds to laminin, a major component of basement membranes. Therefore, the protein was called M. smegmatis laminin-binding protein (MS-LBP). MS-LBP does not appear to be involved in adherence in the absence of laminin but is responsible for the laminin-mediated mycobacterial adherence to human pneumocytes and macrophages. Homologous laminin-binding adhesins are also produced by virulent mycobacteria such as M. tuberculosis and Mycobacterium leprae, suggesting that this adherence mechanism may contribute to the pathogenesis of mycobacterial diseases.
Pethe
K
K
INSERM U447, Mécanismes Moléculaires de la Pathogénie Microbienne, Institut Pasteur de Lille, 1 Rue A. Calmette, 59019 Lille Cedex, France.
Puech
V
V
Daffé
M
M
Josenhans
C
C
Drobecq
H
H
Locht
C
C
Menozzi
F D
FD
D000907:Antibodies, Bacterial / Q000276:immunology; D001422:Bacterial Adhesion; D002451:Cell Compartmentation; D003001:Cloning, Molecular; D003429:Cross Reactions; D000939:Epitopes; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D006031:Glycosylation; D006657:Histones / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D008264:Macrophages / Q000382:microbiology; D016253:Microscopy, Immunoelectron; D009164:Mycobacterium Infections / Q000209:etiology; D020102:Mycobacterium smegmatis / Q000276:immunology*; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D011650:Pulmonary Alveoli / Q000382:microbiology; D017474:Receptors, Laminin / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification
D000907:Antibodies, Bacterial; D000939:Epitopes; D006657:Histones; D017474:Receptors, Laminin