Open AccessDetection of prokaryotic signal peptidase in an Escherichia coli membrane fraction: endoproteolytic cleavage of nascent f1 pre-coat protein.
Author(s) -
Chung Nan Chang,
Günter Blobel,
Peter Model
Publication year - 1978
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.75.1.361
Subject(s) - signal peptidase , cleavage (geology) , escherichia coli , biology , biochemistry , signal peptide , peptide sequence , membrane protein , polyacrylamide gel electrophoresis , amino acid , membrane , enzyme , paleontology , fracture (geology) , gene
An inverted membrane vesicle fraction isolated from uninfected Escherichia coli and largely derived from the inner membrane has been shown to contain an endoproteolytic activity that cleaves nascent bacteriophage f1 pre-coat protein into two identifiable products. The electrophoretic mobility on sodium dodecyl sulfate/urea/polyacrylamide gels and the partial amino-terminal sequence of the larger fragment were indistinguishable from those of the mature phage coat protein. Partial amino-terminal sequence analysis showed that the smaller fragment corresponds to the amino-terminal "signal peptide" of f1 pre-coat protein. Cleavage occurred only if the membrane fraction was present during in vitro synthesis, and was not observed if it was added after completion of pre-coat protein synthesis. The cleavage reaction was strongly stimulated when the membrane fraction was present together with the nonionic detergent Nikkol. These results are consistent with and discussed in terms of the signal hyothesis.