Tolerance of Escherichia coli beta-galactosidase C-terminus to different-sized fusions

The tolerance of the beta-galactosidase C-terminus to foreign protein fusio ns has been explored by using different-sized derivatives of the chimeric p rotein LACVP1. While the molecular mass of the partner domain shows a minor influence on protein toxicity for the producing E. coil cells, it dramatic ally affects the proteolytic susceptibility of the whole fusion. Surprising ly, the observed structural modulation of proteolysis is not an all-or-noth ing process, but it exhibits a continuous effect concomitantly with the len gth of the fusion. The conformational effects caused by increasingly sized partners seem to progressively expose cryptic protease target sites, initia ting a proteolytic cascade that dramatically reduces the yield of the recom binant protein. (C) 1999 John Wiley & Sons, Inc.