High resolution X-ray structure and potent anti-HIV activity of recombinant dianthin antiviral protein

Dianthin antiviral protein (DAP) is a naturally occurring antiviral protein from the leaves of carnation (Dianthus caryophyllus) capable of depurinating HIV-1 RNA and inhibiting HIV-1 replication in human peripheral blood mononuclear cells. Escherichia coli-derived recombinant DAP (rDAP, amino acids 1-254) was purified to homogeneity for structural and functional studies. In the following paper the X-ray crystal structure of rDAP as well as its complexes with cyclic AMP and adenyl-guanosine (ApG) as substrate analogs at 1.7 A resolution are reported. Molecular modeling studies of the interactions of DAP and the structurally similar pokeweed antiviral protein (PAP) with a single-stranded RNA heptamer predicted a more potent anti-HIV activity for rDAP due to its unique surface topology and more favorable charge distribution in its 20 A-long RNA binding active center cleft. In accordance with the predictions of the modeling studies, rDAP was more potent than rPAP in depurinating HIV-1 RNA. To the knowledge of the authors, this is the first structural and functional characterization of recombinant DAP.