POLYLINKER-ENCODED PEPTIDES CAN CONFER TOXICITY TO RECOMBINANT PROTEINS PRODUCED IN ESCHERICHIA-COLI

Three DNA segments encoding fragments of the p60 capsid protein of rab bit haemorrhagic disease virus (RHDV) have been cloned and expressed i n Escherichia coli. The cDNAs were placed under the control of the T7 promoter in a pET-derived expression vector designed to produce C-term inal histidine tail fusions. By using different cloning strategies, ce ll toxicity exhibited by some of the expressed products was dramatical ly affected, coincident with minor modifications in the carboxy termin us sequences of the recombinant proteins. In particular, the presence of a nonhydrophobic peptide encoded by polylinker sequences promotes c ell death and a reduced yield after induction of gene expression, wher eas a histidine tail has no detectable effect. These data point out th e critical role that needless peptide tails, accidentally introduced i nto recombinant proteins by nonrelevant DNA stretches, can have on pro tein expression and final yield of a production process.