Biosynthesis of Escherichia coli Braun's Lipoprotein Precursors in vitro and Binding to Membrane Vesicles

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Abstract
A cell-free system only programmed by endogenous E. coli mRNA present in a 30,000 .times. g supernatant fraction is described in which 15-40% of the material produced was constituted by 2 lipoprotein precursors. These 2 polypeptides are immunologically related, contain the signal peptide and apparently differ by the presence in one of them of a substituent on the SH group of the single cysteine residue. The nature of this substituent could not be determined, but no evidence was obtained that it could be a glyceride. No processing of any of these prolipoprotein forms could be demonstrated by the addition of Triton X-100 or membrane vesicles. A similar binding of both precursors to inverted membrane vesicles was observed when they were provided co-translationally or post-translationally, and this reaction occurred without the help of major membrane compounds.