Aminoacylation of the N-terminal cysteine is essential for Lol-dependent release of lipoproteins from membranes but does not depend on lipoprotein sorting signals.
Lipoproteins are present in a wide variety of bacteria and are anchored to membranes through lipids attached to the N-terminal cysteine. The Lol system of Escherichia coli mediates the membrane-specific localization of lipoproteins. Aspartate at position 2 functions as a Lol avoidance signal and causes the retention of lipoproteins in the inner membrane, whereas lipoproteins having residues other than aspartate at position 2 are released from the inner membrane and localized to the outer membrane by the Lol system. Phospholipid:apolipoprotein transacylase, Lnt, catalyzes the last step of lipoprotein modification, converting apolipoprotein into mature lipoprotein. To reveal the importance of this aminoacylation for the Lol-dependent membrane localization, apolipoproteins were prepared by inhibiting lipoprotein maturation. Lnt was also purified and used to convert apolipoprotein into mature lipoprotein in vitro. The release of these lipoproteins was examined in proteoliposomes. We show here that the aminoacylation is essential for the Lol-dependent release of lipoproteins from membranes. Furthermore, lipoproteins with aspartate at position 2 were found to be aminoacylated both in vivo and in vitro, indicating that the lipoprotein-sorting signal does not affect lipid modification.
Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
Ayumu
A
Fukuda
Shin-Ichi
S
Matsuyama
Takashi
T
Hara
Jiro
J
Nakayama
Hiromichi
H
Nagasawa
Hajime
H
Tokuda
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000215:Acylation; D001224:Aspartic Acid; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D003545:Cysteine; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D008074:Lipoproteins / Q000378:metabolism*; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000378:metabolism*; D033902:Periplasmic Binding Proteins / Q000378:metabolism*; D010957:Plasmids; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction
D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D008074:Lipoproteins; C116111:LolA protein, E coli; C407982:LolC protein, E coli; C407983:LolD protein, E coli; C407984:LolE protein, E coli; D008565:Membrane Proteins; D033902:Periplasmic Binding Proteins; D011994:Recombinant Proteins; D001224:Aspartic Acid; D003545:Cysteine