The streptokinase (SK) gene from S. equisimilis H46A (ATCC 12449) was clone
d in E. coli W3110 under the control of the tryptophan promoter. The recomb
inant SK, which represented 15% of total cell protein content, was found in
the soluble fraction of disrupted cells. The solubility of this SK notably
differed from that of the product of the SK gene from S. equisimilis (ATCC
9542) which had been cloned in E. coli W3110 by using similar expression v
ector and cell growth conditions, and occurred in the form of inclusion bod
ies.