ISOLATION AND PARTIAL CHARACTERIZATION OF NIGRIN-B, A NONTOXIC NOVEL TYPE-2 RIBOSOME-INACTIVATING PROTEIN FROM THE BARK OF SAMBUCUS-NIGRA L

The bark of Sambucus nigra L. contains a non-toxic novel type 2 ribosome-inactivating protein that we named nigrin b. In vitro, nigrin b strongly inhibited mammalian protein synthesis but did not affect plant nor bacterial protein synthesis. The protein (M(r) 58 000) contains two subunits, A (M(r) 26 000) and B (M(r) 32 000); linked by disulphide bridge(s). Nigrin b was found to be an rRNA N-glycosidase of the rRNA of intact mammalian ribosomes and shares a very good N-terminal amino-acid sequence homology with the anti-HIV-1 proteins TAP 29 and trichosanthin.