Bacterial glycoproteins: a link between glycosylation and proteolytic cleavage of a 19 kDa antigen from Mycobacterium tuberculosis

• Published in: The EMBO journal Vol. 15; no. 14; pp. 3547 - 3554
• Main Authors: Herrmann, J. L., O'Gaora, P., Gallagher, A., Thole, J. E., Young, D. B.
• Format: Journal Article
• Language: English
• Published: England 15-07-1996
• Subjects: Alkaline Phosphatase - genetics; Amino Acid Sequence; Bacterial Proteins - metabolism; Binding Sites; Concanavalin A - metabolism; Endopeptidases - metabolism; Glycoproteins - metabolism; Glycosylation; Molecular Sequence Data; Mutagenesis, Site-Directed; Mycobacterium tuberculosis; Mycobacterium tuberculosis - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sequence Homology, Amino Acid
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1996.tb00724.x

Protein glycosylation has an important influence on a broad range of molecular interactions in eukaryotes, but is comparatively rare in bacteria. Several antigens from Mycobacterium tuberculosis, the causative agent of human tuberculosis, have been identified as glycoproteins on the basis of lectin binding, or by detailed structural analysis. By production of a set of alkaline phosphatase (PhoA) hybrid proteins in a mycobacterial expression system, the peptide region required for glycosylation of the 19 kDa lipoprotein antigen from M.tuberculosis was defined. Mutagenesis of two threonine clusters within this region abolished lectin binding by PhoA hybrids and by the 19 kDa protein itself. Substitution of the threonine residues also resulted in generation of a series of smaller forms of the protein as a result of proteolysis. In a working model to account for these observations, we propose that the role of glycosylation is to regulate cleavage of a proteolytically sensitive linker region close to the acylated N‐terminus of the protein.