Bacterial Lipoproteins; Biogenesis, Virulence/Pathogenicity and Trafficking
Hajime Tokuda, Peter Sander, Bok Luel Lee, Suguru Okuda, Thomas Grau, Andreas Tschumi, Juliane K. Brülle, Kenji Kurokawa and Hiroshi Nakayama
from: Bacterial Membranes: Structural and Molecular Biology (Edited by: Han Remaut and Rémi Fronzes). Caister Academic Press, U.K. (2014)
The mechanisms underlying the biogenesis and outer membrane sorting of lipoproteins have been mostly clarified in Escherichia coli. Three enzymes catalyze the post-translational modification of lipoproteins with a membrane anchor comprising a thioether-linked diacylglycerol and an amide linked fatty acid. The Lol system comprising five Lol proteins mediates the sorting of lipoproteins to the outer membrane. The three enzymes and five proteins are essential for E. coli and are widely conserved in Gram-negative diderms having cytoplasmic and outer membranes. High G+C content Gram-positive bacteria such as those belonging to the genera Mycobacterium and Corynebacterium have an outer membrane-like structure. The structure and biogenesis of the cell envelope have been intensively studied in mycobacterial species including medically important Mycobacterium tuberculosis. Mycobacterial lipoproteins are triacylated, like those of Gram-negative diderms. The enzyme catalyzing N-acylation was recently identified. The lipoprotein biosynthesis pathway is important for virulence of M. tuberculosis. The functions of individual mycobacterial lipoproteins are discussed in relation to envelope biogenesis, virulence and influence on immune systems. The N-terminal structures of lipoproteins of low G+C content Gram-positive monoderms are surprisingly diverse. An enzyme catalyzing the N-acylation of the N-terminal Cys of lipoproteins has not been found in this class of bacteria. However, lipoproteins of Staphylococcus species are N-acylated. Moreover, three novel structures of lipidated N-terminal Cys were revealed on mass spectrometric analyses. A possible biosynthetic pathway generating these structures is discussed read more ...