Fig. 5. Biotinylation of surface proteins in E. coli. (a) Representative immunoblots of Pal from E. coli K1 RS218: nonbiotinylated Pal (A) and Sulfo-NHS-SS-biotinylated Pal (B); nonbiotinylated Pal (C) and NHS-LC-LC-biotinylated Pal (D). (b) The immunoblot for alkaline phosphatase from E. coli K1 RS218 shows that all of the protein is nonbiotinylated (A) and no biotinylated protein (by NHS-LC-LC-biotin) was detected (B). (c) The immunoblot for RNA polymerase β from E. coli K1 RS218 shows that only a very small percentage of RNA polymerase β is biotinylated with NHS-LC-LC-biotin (14 %) (B) or Sulfo-NHS-SS-biotin (5 %) (D), while most of RNA polymerase β is nonbiotinylated (A, C).