Sorting of Bacterial Lipoproteins to the Outer Membrane by the Lol System

  • Shin-ichiro Narita
  • Hajime Tokuda
Part of the Methods in Molecular Biology book series (MIMB, volume 619)


Bacterial lipoproteins comprise a subset of membrane proteins with a lipid-modified cysteine residue at their amino termini through which they are anchored to the membrane. In Gram-negative bacteria, lipoproteins are localized on either the inner or the outer membrane. The Lol system is responsible for the transport of lipoproteins to the outer membrane.

The Lol system comprises an inner-membrane ABC transporter LolCDE complex, a periplasmic carrier protein, LolA, and an outer membrane receptor protein, LolB. Lipoproteins are synthesized as precursors in the cytosol and then translocated across the inner membrane by the Sec translocon to the outer leaflet of the inner membrane, where lipoprotein precursors are processed to mature lipoproteins. The LolCDE complex then mediates the release of outer membrane-specific lipoproteins from the inner membrane while the inner membrane-specific lipoproteins possessing Asp at position 2 are not released by LolCDE because it functions as a LolCDE avoidance signal, causing the retention of these lipoproteins in the inner membrane. A water-soluble lipoprotein–LolA complex is formed as a result of the release reaction mediated by LolCDE. This complex traverses the hydrophilic periplasm to reach the outer membrane, where LolB accepts a lipoprotein from LolA and then catalyzes its incorporation into the inner leaflet of the outer membrane.

Key words

Lipoprotein outer membrane Lol system ABC transporter spheroplasts reconstitution Escherichia coli 



We wish to thank Rika Ishihara for the help in the preparation of this chapter. The work described here was supported by grants to H. T. from the Ministry of Education, Science, Sports, and Culture of Japan.


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Shin-ichiro Narita
    • 1
  • Hajime Tokuda
    • 1
  1. 1.Institute of Molecular and Cellular BiosciencesUniversity of TokyoTokyoJapan

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