CHARACTERIZATION OF AN ESCHERICHIA-COLI ROTA MUTANT, AFFECTED IN PERIPLASMIC PEPTIDYL-PROLYL CIS TRANS ISOMERASE/

The rotA gene of Escherichia coli encodes a peptidylprolyl cis/trans i somerase (PPlase), which is supposed to catalyse protein folding in th e periplasm. To investigate the importance of the enzyme, the rotA gen e was cloned and a chromosomal deletion mutant was created. The rotA m utant was normally viable. No residual PPlase activity could be detect ed in the periplasmic fraction of the mutant, Comparison of the patter ns of periplasmic and outer membrane proteins by SDS-PAGE revealed no differences in protein composition between the rotA mutant and its par ental strain. Similarly, the kinetics of periplasmic protein folding a nd outer membrane protein assembly appeared unaffected by the rotA mut ation. Our results show that the periplasmic PPlase of E. coli is not essential and that the protein does not play an important role in prot ein folding.