Secretion of a prokaryotic cellulase in bacterial and mammalian cells

The catalytic domain of mature Clostridium thermocellum endoglucanase E (EGE') and derivatives of the enzyme fused to prokaryote and eukaryote signal peptides (SP), were produced in Chinese hamster ovary (CHO) cells and Escherichia coli. All three forms of the endoglucanase were secreted into the periplasm of Escherichia coli, but only derivatives of the enzyme containing an N-terminal SP were exported from CHO cells. Extracellular EGE', purified from E. coli and CHO cultures, displayed similar properties suggesting that glycosylation of the enzyme in the eukaryote did not significantly alter the protein's properties. Data presented in this report indicate that mature EGE' contains secretion signals which are recognised only by the E. coli protein export apparatus, suggesting that there are differences in the recognition of certain secretion signals in eukaryotes and prokaryotes. As mature EGE' does not contain secretion signals recognised by the mammalian cell, membrane translocation of the bacterial cellulase in a higher eukaryote is directed by an N-terminal prokaryotic SP.