title: A new activity of anti-HIV and anti-tumor protein GAP31: DNA adenosine glycosidase--structural and modeling insight into its functions.
abstract: We report here the high-resolution atomic structures of GAP31 crystallized in the presence of HIV-LTR DNA oligonucleotides systematically designed to examine the adenosine glycosidase activity of this anti-HIV and anti-tumor plant protein. Structural analysis and molecular modeling lead to several novel findings. First, adenine is bound at the active site in the crystal structures of GAP31 to HIV-LTR duplex DNA with 5' overhanging adenosine ends, such as the 3'-processed HIV-LTR DNA but not to DNA duplex with blunt ends. Second, the active site pocket of GAP31 is ideally suited to accommodate the 5' overhanging adenosine of the 3'-processed HIV-LTR DNA and the active site residues are positioned to perform the adenosine glycosidase activity. Third, GAP31 also removes the 5'-end adenine from single-stranded HIV-LTR DNA oligonucleotide as well as any exposed adenosine, including that of single nucleotide dAMP but not from AMP. Fourth, GAP31 does not de-purinate guanosine from di-nucleotide GT. These results suggest that GAP31 has DNA adenosine glycosidase activity against accessible adenosine. This activity is distinct from the generally known RNA N-glycosidase activity toward the 28S rRNA. It may be an alternative function that contributes to the antiviral and anti-tumor activities of GAP31. These results provide molecular insights consistent with the anti-HIV mechanisms of GAP31 in its inhibition on the integration of viral DNA into the host genome by HIV-integrase as well as irreversible topological relaxation of the supercoiled viral DNA.
authors.affiliation: Department of Biochemistry, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Hui-Guang
authors.initials: HG
authors.lastname: Li
authors.forename: Philip L
authors.initials: PL
authors.lastname: Huang
authors.forename: Dawei
authors.initials: D
authors.lastname: Zhang
authors.forename: Yongtao
authors.initials: Y
authors.lastname: Sun
authors.forename: Hao-Chia
authors.initials: HC
authors.lastname: Chen
authors.forename: John
authors.initials: J
authors.lastname: Zhang
authors.forename: Paul L
authors.initials: PL
authors.lastname: Huang
authors.forename: Xiang-Peng
authors.initials: XP
authors.lastname: Kong
authors.forename: Sylvia
authors.initials: S
authors.lastname: Lee-Huang
mesh_terms: D000225:Adenine / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000494:pharmacology; D001483:Base Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D045647:DNA Glycosylases / Q000737:chemistry* / Q000494:pharmacology; D004279:DNA, Viral / Q000187:drug effects / Q000235:genetics; D019428:HIV Integrase Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D016325:HIV Long Terminal Repeat; D006801:Humans; D008958:Models, Molecular; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011487:Protein Conformation; D054789:Ribosome Inactivating Proteins, Type 1 / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship; D016662:Virus Integration / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D004279:DNA, Viral; C071380:GAP31 protein, Gelonium multiflorum; D019428:HIV Integrase Inhibitors; D009838:Oligodeoxyribonucleotides; D054789:Ribosome Inactivating Proteins, Type 1; D045647:DNA Glycosylases; D000225:Adenine