ISSN:
1432-0614
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Summary Because induction of proteolytic activity and stress-response proteins can significantly affect expression levels in recombinant Escherichia coli, the influence of low-level expression of a mutant \-galactosidase was investigated. A single copy of the well-characterized CSH11 mutant of the lacZ gene was integrated into the chromosome. Induction of expression of the mutant \-galactosidase caused a measurable increase in ATP-dependent intracellular proteolytic activity but resulted in no significant change in ATP-independent proteolytic activity. Growth at temperatures above 40°C resulted in a significant decrease in the level of ATP-independent proteolytic activity compared to growth at 37°C, and the ATP-dependent activity increased 2.5-fold from 30 to 42°C. Synthesis of stress-response proteins was evident in two-dimensional gel electrophoresis analysis of proteins in the strain expressing the abnormal \-galactosidase at 37°C, but no such response was evident when mutant \-galactosidase expression was induced at 30°C. In separate experiments, stress proteins were overexpressed by inducing expression of the htpR gene on a plasmid. Resulting increases in stress-protein levels correlated with an increase in ATP-dependent proteolytic activity with no significant change in the intracellular ATP-independent proteolytic activity. These data suggest that even very low levels of abnormal protein can substantially influence protease levels and stress response in E. coli. These responses were reduced by induction' at lower temperatures.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00210989
