Fig. 4.
Surface accessibility of LPS. Shown are silver-stained Tricine-SDS/PAGE gels containing samples treated with proteinase K before loading. (A) Equal amounts of proteinase K-treated cell lysates of the indicated strains were loaded on the same gel. (B) Cell envelopes of bacteria grown the presence or absence of CMP-NANA. Where indicated, the cell envelopes were treated with neuraminidase before electrophoresis. (C) Intact bacteria grown in the presence of CMP-NANA were treated with neuraminidase and subsequently processed for Tricine-SDS/PAGE. In B and C, five times as much material of the imp mutant samples, based on protein content or OD, was loaded compared with wild-type samples. Gels containing the imp mutant samples were developed longer to obtain optimal visibility of the LPS bands. (D) The inducible lpxA mutant was grown in the presence of the IPTG concentrations indicated plus CMP-NANA. Intact cells were treated with neuraminidase as indicated. Equal amounts of cell lysates, based on OD, were analyzed on the same gel.