Cloning and expression of a gene encoding gelonin, a ribosome-inactivating protein from Gelonium multiflorum

A cDNA copy of the gel gene, encoding gelonin (Gel), has been cloned from the seeds of the Asian plant, Gelonium multiflorum. Gel is a type-I ribosome-inactivating protein which has been produced in Escherichia coli as a secreted protein under the transcriptional control of the Salmonella typhimurium araB promoter and linked to the pectate lyase (pelB) leader sequence from Erwinia carotovora. Recombinant, soluble Gel (re-Gel) can be recovered from the E. coli culture supernatant at a yield of greater than 1 mg/ml, and it inhibits protein synthesis in vitro to the same extent as the native protein isolated from plant seeds.