The selective roles of chaperone systems on over-expression of human-like collagen in recombinant Escherichia coli.

Human-like collagen (HLC) is a novel biomedical material with promising applications. Usually, insoluble HLC was formed due to over-expression. In order to improve the production of soluble HLC, the effective chaperone proteins and their mediation roles on HLC were clarified. Trigger factor (TF) pathway with low specificity and high binding affinity to nascent chains could increase soluble HLC expression; GroEL-GroES could increase the expression level of HLC by assisting the correct folding of HLC and increase mRNA level of the gene coding for HLC by enhancing mRNA stability. DnaK chaperone system did not work positively on soluble HLC due to the unbalanced ratio of DnaK:DnaJ:GrpE, especially too high GrpE significantly inhibited DnaK-mediated refolding. The production of soluble HLC with co-expression of exogenous TF and GroEL-GroES was increased by 35.3 % in comparison with the highest value 0.26 g/L reported previously.