Efficient production of N-terminally truncated biologically active human interleukin-6 by Bacillus brevis

cDNAs encoding human interleukin 6 (hIL-6) and its variants lacking the N-t erminal Pro and Pro-Val-Pro-Pro, respectively, were expressed in Bacillus b revis by using the signal peptide fusion approach. The presence of Pro at t he N-terminus of the mature protein hindered the action of the Bacillus bre vis signal peptidase. hIL-6 lacking the N-terminal Pro-Val-Pro-Pro was most efficiently secreted in a biologically active form and accumulated in the culture medium to a level of 200 mg per liter, which is the highest level r eported for the bacterial secretion of hIL-6.