Cold shock induction of recombinant Arctic environmental genes.
BACKGROUND
Heterologous expression of psychrophilic enzymes in E. coli is particularly challenging due to their intrinsic instability. The low stability is regarded as a consequence of adaptation that allow them to function at low temperatures. Recombinant production presents a significant barrier to their exploitation for commercial applications in industry.


METHODS
As part of an enzyme discovery project we have investigated the utility of a cold-shock inducible promoter for low-temperature expression of five diverse genes derived from the metagenomes of marine Arctic sediments. After evaluation of their production, we further optimized for soluble production by building a vector suite from which the environmental genes could be expressed as fusions with solubility tags.


RESULTS
We found that the low-temperature optimized system produced high expression levels for all putatively cold-active proteins, as well as reducing host toxicity for several candidates. As a proof of concept, activity assays with one of the candidates, a putative chitinase, showed that functional protein was obtained using the low-temperature optimized vector suite.


CONCLUSIONS
We conclude that a cold-shock inducible system is advantageous for the heterologous expression of psychrophilic proteins, and may also be useful for expression of toxic mesophilic and thermophilic proteins where properties of the proteins are deleterious to the host cell growth.
Norstruct, Department of Chemistry, Faculty of Science and Technology, University of Tromsø, N-9037, Tromsø, Norway. gro.bjerga@uni.no.|Centre for Applied Biotechnology, Uni Research AS, Thormøhlensgt. 55, N-5008, Bergen, Norway. gro.bjerga@uni.no.
Gro Elin Kjæreng
GE
Bjerga
Norstruct, Department of Chemistry, Faculty of Science and Technology, University of Tromsø, N-9037, Tromsø, Norway. adele.k.williamson@uit.no.
Adele Kim
AK
Williamson
D000220:Adaptation, Biological / Q000235:genetics*; D001110:Arctic Regions; D002688:Chitinases / Q000378:metabolism; D003001:Cloning, Molecular; D003080:Cold Temperature; D058639:Cold-Shock Response / Q000502:physiology*; D004790:Enzyme Induction / Q000502:physiology*; D004798:Enzymes / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli; D005822:Genetic Vectors / Q000235:genetics; D019015:Geologic Sediments / Q000382:microbiology*; D054892:Metagenome / Q000235:genetics*; D009792:Oceans and Seas; D011994:Recombinant Proteins / Q000378:metabolism
D004798:Enzymes; D011994:Recombinant Proteins; D002688:Chitinases