TAILIEUCHUNG - Báo cáo khoa học: Dissection of LolB function – lipoprotein binding, membrane targeting and incorporation of lipoproteins into lipid bilayers

Escherichia colicells express at least 90 species of lipoprotein. LolB is one of the essential outer membrane lipoproteins, being involved in the last step of lipoprotein sorting. It accepts lipoproteins from a periplasmic molecular chaperone, LolA, and mediates the outer membrane anchoring of lipopro-teins through a largely unknown mechanism. It has been shown previously that a LolB derivative, mLolB, lacking an N-terminal acyl chain, can bind lipoproteins. | ễFEBS Journal Dissection of LolB function - lipoprotein binding membrane targeting and incorporation of lipoproteins into lipid bilayers Jun Tsukahara Keita Mukaiyama Suguru Okuda Shin-ichiro Narita and Hajime Tokuda Institute of Molecular and Cellular Biosciences University of Tokyo Japan Keywords lipoprotein LolA LolB membrane targeting phospholipids Correspondence H. Tokuda Institute of Molecular and Cellular Biosciences University of Tokyo 1-1-1 Yayoi Bunkyo-ku Tokyo 113-0032 Japan Fax 81 3 5841 8464 Tel 81 3 5841 7830 E-mail htokuda@ Received 1 May 2009 revised 1 June 2009 accepted 16 June 2009 doi Escherichia coli cells express at least 90 species of lipoprotein. LolB is one of the essential outer membrane lipoproteins being involved in the last step of lipoprotein sorting. It accepts lipoproteins from a periplasmic molecular chaperone LolA and mediates the outer membrane anchoring of lipoproteins through a largely unknown mechanism. It has been shown previously that a LolB derivative mLolB lacking an N-terminal acyl chain can bind lipoproteins. We examined how the lack of an N-terminal anchor affects the outer membrane anchoring of lipoproteins. Surprisingly mLolB compensates for LolB function and supports E. coli growth indicating that the N-terminal anchor is not essential for its function. Indeed mLolB correctly localizes lipoproteins to either the inner or outer membrane depending on the sorting signal at the steady state. Furthermore periplasmic mLolB enables the dissection of LolB function namely lipoprotein binding membrane targeting and lipoprotein anchoring. It mediates the transfer of lipoproteins from LolA to the outer membrane but also the inner membrane and liposomes indicating that mLolB exhibits no membrane preference and targets to phospholipids. Consequently an outer membrane-specific lipoprotein is transiently mislocalized to the inner membrane when cells express only mLolB. LolB anchored to

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