To identify and provide proteins each having such a general function as to isolate from cell membrane and deliver to localization mechanism (LolA- LolB mechanism) to outer membrane a matured lipoprotein after processing in microorganisms belonging to Gram-negative bacteria.

The protein, proteins (LolC, LolD and LolE) each having the function to control the localization of a lipoprotein in Escherichia coli, are identified, and their amino acid sequences are identified respectively. These amino acid sequences are compared, on a database, with the gene arrangements of other Gram-negative bacteria and the corresponding homologous proteins are searched. By controlling the expression of the objective protein, it is hopeful of raising the secretive production efficiency of useful protein using microorganisms; and by searching a substance capable of specifically inhibiting the function, it is thought that antibacterial agents for Gram-negative bacteria can efficiently be obtained; furthermore, using antibodies to the above proteins, it is also hopeful of constructing a specific detective system for Gram-negative bacteria.