Lipobox - Structural determinant for bacterial lipid modification
Bacterial Lipoproteins are synthesized as any other normal membrane protein with a signal sequence . However, analysis of the signal sequences of different lipoproteins revealed common structural features that are recognized prior to lipid modification. The most important of all is the presence of a distinct sequence at the C-terminal end of the signal peptide, referred to as lipobox . The amino acid distribution in a lipobox is shown in the figure below.
The lipobox contains the invariant Cys that is lipid-modified and the -3 position is mainly Leu. The consensus sequence being [LVI][ASTVI][GAS][C]. Apart from the lipobox the N-terminal 5-7 residues with mostly 2 positively charged Lys or Arg residues and the intervening stretch of hydrophobic and uncharged residues of 7-22 amino acid length are important. These features are used to identify lipoproteins in protein data base. One such program is available in this site and we welcome you to submit your sequence in the analysis page to identify probable lipoprotein signal peptide in the given protein.
1) Inouye, S., Wang, S., Sekizawa, J., Halegoua, S.,
and Inouye, M., Amino acid sequence for the peptide extension on
the prolipoprotein of the Eschericia coli outer membrane, Proc.
Natl. acad. Sci. U. S. A., 74, 1004, 1977.
2) Sankaran, K. and Wu, H. C. "Bacterial lipoproteins" in Lipid Modifications of Proteins Ed. M. J. Schlesinger , CRC Press, Boca Raton, Ann Arbor, London, Tokyo. Ch. 6, P. 163, 1993.
3) Braun, V., and H. C. Wu. 1993. Lipoproteins, structure, function, biosynthesis and model for protein export, p. 319 - 342. In J-M Ghuysen and R. Hakenback (ed), Comprehensive biochemistry, vol 27. Bacterial cell wall. Elsevier Science Publishers, B.V.Amsterdam
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