SummaryThe LolCDE complex of Escherichia coli belongs to the ABC transporter superfamily and initiates the lipoprotein sorting to the outer membrane by catalysing their release from the inner membrane. LolC and/or LolE, membrane subunits, recognize lipoproteins anchored to the outer surface of the inner membrane, while LolD hydrolyses ATP on its inner surface. We report here that ligand-bound LolCDE can be purified from the inner membrane in the absence of ATP.

A calcium-sensitive cls4 mutant of Saccharomyces cerevisiae ceased dividing in the presence of 100 mM CaC12, producing large, round, unbudded cells. Since its DNA replication and nuclear division still continued after interruption of normal budding, the cls4 mutant had a defect in bud formation in Ca2+-rich medium. Its calcium content and calcium uptake activity were the same as those of the wild-type strain, suggesting that the primary defect of the mutation was not in a Ca2+ transport system. Genetic analysis showed that the cls4 mutation did not complement the cdc24-1 mutation, which is known to be a temperature-sensitive mutation affecting bud formation and localized cell surface growth at a restrictive temperature. Moreover, cls4 was tightly linked to cdc24, and a yeast 3.4-kilobase-pair DNA fragment carrying both the CLS4 and CDC24 genes was obtained. These results suggest that the cls4 mutation is allelic to the cdc24 mutation. Thus, Ca2+ ion seems to control bud formation and bud-localized cell surface growth.

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