Mutations which alter the function of the signal sequence of the maltose binding protein of Escherichia coli

Abstract
The maltose binding protein of E. coli is secreted into the external periplasmic compartment of the cell by virtue of an amino-terminal signal sequence. Using DNA sequencing, the precise nature of mutations in the signal sequence was determined which prevent the export of the maltose binding protein, causing it to accumulate in the cytoplasm in its precursor form. In most cases, the change of a single hydrophobic or uncharged amino acid to a charged amino acid within the signal sequence is sufficient to block the secretion process.