Abstract
The identification of a plasmid-bearing strain of E. coli that overproduces leader peptidase 4- to 6-fold is reported. This strain grows normally and shows an unaltered polypeptide composition of inner and outer membranes. The leader peptidase gene was subcloned and transferred from this plasmid to the multicopy plasmid pBR322, yielding a new plasmid (pTD101). Strains transformed by pTD101 have a 30-fold increase in leader peptidase. The effect of leader peptidase overproduction on the insertion of newly made phage M13 coat protein into the plasma membrane of infected cells was studied. The overproducer strain, when infected by phage M13, shows a dramatic acceleration in the conversion of procoat (a cytoplasmic precursor form) to coat (an integral, transmembrane protein). The leader peptidase that converts M13 procoat to coat in vitro can also catalyze this reaction in vivo.

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