HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 (HIV-1) INHIBITION, DNA-BINDING, RNA-BINDING, AND RIBOSOME INACTIVATION ACTIVITIES IN THE N-TERMINAL SEGMENTS OF THE PLANT ANTI-HIV PROTEIN GAP31

GAP31 (gelonium anti-HIV protein of 31 kDa) is an anti-HIV protein whi ch we have identified and purified from a medicinal plant, Gelonium mu ltiflorum. It is capable of inhibiting HIV-1 infection and replication . GAP31 also exhibits DNA topoisomerase inhibitor activity and RNA N-g lycosidase activity. The ability of GAP31 to interrupt both DNA and RN A functions may be related to its multiple antiviral actions. To defin e the roles of these activities in the anti-HIV action of GAP31, a ser ies of peptides corresponding to the N-terminal segment of GAP31 were synthesized and assayed for the aforementioned activities of the paren t molecule. A 33-aa segment (KGATYITYVNFLNELRVKTKPEGNSHGIPSLRK) design ated as K10-K42 is the shortest peptide necessary and sufficient for H IV-1 inhibition, DNA and RNA binding, and ribosome inactivation. The p eptides were 2-5 orders of magnitude less active than GAP31. Truncatio n of 19 aa from the C terminus of K10-K42 resulted in the loss of all of these activities. On the other hand, deletion of N-terminal residue s to give E23-K42 did not alter ribosome-inactivation activity but eli minated the other activities. These findings permit identification of a 7-aa sequence, KGATYIT, at the N terminus of K10-K42 that is critica l for DNA binding and RNA binding, whereas a 9-aa sequence, SHGIPSLRK, at the C terminus is important to ribosome inactivation. Both regions contribute to anti-HIV activity. Histidine at position 35 is critical for all of these activities. The disparity of sequence requirements f or inhibition of HIV infection and replication and for ribosome-inacti vation activity suggests that the anti-HIV activity of most ribosome-i nactivating proteins may not be the result of N-glycosidase activity a lone. Mapping the minimal domain of GAP31 offers insights into the rat ional design of molecular mimetics of anti-HIV drugs.