Correlation of competence for export with lack of tertiary structure of the mature species: a study in vivo of maltose-binding protein in E. coli.

Sensitivity to proteolytic degradation was used to monitor folding of polypeptides in vivo. A correlation between competence for export and lack of stable tertiary structure was established by comparing the kinetics of folding of mutated precursor maltose-binding protein that carries a defective leader peptide with the kinetics of folding of wild-type precursor that is competent for export. It is proposed that during export a kinetic competition exists between productive translocation and folding of precursor intracellularly into a stable conformation that is not compatible with transfer.