Failure of E. coli K-12 to transport PhoE-LacZ hybrid proteins out of the cytoplasm.
A phoE-lacZ hybrid gene encoding the N-terminal 300 amino acid residues of pre-PhoE protein, fused to an almost complete beta-galactosidase molecule was constructed in vitro. Cell fractionation experiments suggested that the hybrid gene product is transported to the outer membrane. However, by using immuno-cytochemical labelling on ultra-thin cryosections it was shown that the hybrid protein accumulated in the cytoplasm. Thus, it appears that: (i) data on the localization of hybrid proteins merely based on cell fractionation experiments are not reliable, and (ii) either the C-terminal 15% of PhoE protein contain information which is essential for transport, or PhoE-LacZ hybrid proteins can never be transported out of the cytoplasm. The implications of these results for current models on the translocation of outer membrane proteins are discussed.
Tommassen
J
J
Leunissen
J
J
van Damme-Jongsten
M
M
Overduin
P
P
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004262:DNA Restriction Enzymes; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D005796:Genes; D005798:Genes, Bacterial; D007106:Immune Sera; D007118:Immunoassay; D007700:Kinetics; D007763:Lac Operon; D008854:Microscopy, Electron; D010957:Plasmids
D001426:Bacterial Proteins; D007106:Immune Sera; D004262:DNA Restriction Enzymes