Escherichia coli mutants accumulating the precursor of a secreted protein in the cytoplasm

Abstract
The maltose binding protein of E. coli is secreted into the external periplasmic compartment of the cell. A selection procedure for the isolation of mutants which fail to export this protein is described. These mutants probably result from alterations in the amino terminal signal sequence, causing the maltose binding protein produced to accumulate in the cytoplasm in its precursor form.