DEMONSTRATION IN-VIVO THAT INTERACTION OF MALTOSE-BINDING PROTEIN WITH SECB IS DETERMINED BY A KINETIC PARTITIONING

An early step in the export of maltose-binding protein to the periplas m is interaction with the molecular chaperone SecB. We demonstrate tha t binding to SecB in vivo is determined by a kinetic partitioning betw een the folding of maltose-binding protein to its native state and its association with SecB, A complex of SecB and a species of maltose-bin ding protein that folds slowly is shown to be longer-lived than a comp lex of the wild-type maltose-binding protein and SecB. In addition, we show that incomplete nascent chains, which are unable to fold, remain complexed with SecB.