CHAPERONE-MEDIATED ACTIVATION IN-VIVO OF A PSEUDOMONAS-CEPACIA LIPASE

An extracellular Pseudomonas cepacia lipase, LipA, is inactive when ex pressed in the absence of the product of the limA gene. Evidence has b een presented that LimA is a molecular chaperone. The lipA and limA ge nes have been cloned in separate and independently inducible expressio n systems in Escherichia coli. These systems were used to test the mol ecular chaperone hypothesis by investigating whether LimA could activa te presynthesized prelipase and whether presynthesized LimA could acti vate newly synthesized prelipase. The results show that LimA cannot ac tivate presynthesized prelipase and that presynthesized LimA can activ ate only a limited number of de novo synthesized prelipase molecules. Co-immunoprecipitation of prelipase/lipase with LimA generated a 1:1 c omplex of prelipase/lipase and LimA. The results suggest that a 1:1 co mplex of LipA and LimA is required for prelipase processing and secret ion of active lipase.