Genetic analyses of the in vivo function of LolA, a periplasmic chaperone involved in the outer membrane localization of Escherichia coli lipoproteins

The major outer membrane lipoprotein (Lpp) of Escherichia coli is released from the cytoplasmic membrane into the periplasm as a complex with LolA, a periplasmic chaperone, prior to the localization in the outer membrane. To determine whether or not LolA is generally involved in the outer membrane localization of lipoproteins in vivo, the chromosomal lolA gene was manipulated so as to be controlled by the lac promoter-operator. Depletion of LolA caused a severe growth defect, and impaired the outer membrane localization of Lpp and Pal, another outer membrane lipoprotein. Although LolA depletion did not immediately arrest the growth of cells lacking Lpp, disruption of the chromosomal lolA gene was lethal to the lpp strain, indicating that LolA is generally required for the outer membrane localization of lipoproteins, and therefore essential irrespective of the presence or absence of Lpp.