Cloning and expression of recombinant, functional ricin B chain.
The cDNA encoding the B chain of the plant toxin ricin has been cloned and expressed in monkey kidney COS-M6 cells. The recombinant B chain was detected by labeling the transfected cells with [35S]methionine and [35S]-cysteine and demonstrating the secretion of a protein with a Mr of 30,000-32,000 that was not present in the medium of mock-transfected COS-M6 cells. This protein was specifically immunoprecipitated by an anti-ricin or anti-B-chain antibody and the amount of recombinant B chain secreted by the COS-M6 cells was determined by a radioimmunoassay. Virtually all of the recombinant B chain formed active ricin when mixed with native A chain; it could also bind to the galactose-containing glycoprotein asialofetuin as effectively as native B chain. These results indicate that the vast majority of recombinant B chains secreted into the medium of the COS-M6 cells retain biological function.
D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D003545:Cysteine / Q000378:metabolism; D005690:Galactose; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000378:metabolism; D000882:Haplorhini; D008715:Methionine / Q000378:metabolism; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000235:genetics*; D012276:Ricin / Q000235:genetics*
D006023:Glycoproteins; D011994:Recombinant Proteins; D012276:Ricin; D008715:Methionine; D003545:Cysteine; D005690:Galactose