title: Zn2+ binding to cysteine-rich domain of extracellular human immunodeficiency virus type 1 Tat protein is associated with Tat protein-induced apoptosis.
abstract: The Tat protein has several functional domains, one of which is the cysteine-rich domain that is a highly conserved region in spite of the presence of many subtypes of human immunodeficiency virus type 1 (HIV-1). Although the cysteine-rich domain is a potential site for Zn(2+) binding, it is controversial whether Zn(2+) is substantially essential for the structure and activities of the Tat protein. To study the significance of Zn(2+) in the cysteine-rich domain of the Tat protein particularly released to the extracellular space, we raised the monoclonal antibody (MAb) 5A4, which has an attractive property of recognizing the Zn(2+)-binding Tat(20-41) peptide but not the apo-Tat(20-41) peptide. MAb 5A4 inhibited the trans-activation of the HIV long terminal repeat (LTR) in HeLa-CD4-LTR/beta-gal cells induced by treatment with the recombinant Tat protein, indicating that MAb 5A4 can recognize the full-length Tat protein and inhibit its trans-activity. The antibody also inhibited the apoptosis of Jurkat cells induced by treatment with the released native-Tat-protein-containing supernatant from the culture of HIV-1(JRFL)-infected cells. These results suggest that Zn(2+), whose structure is closely associated with not only the trans-activation of HIV-LTR but also the induction of apoptosis, binds to the extracellular native Tat protein. The Zn(2+)-binding cysteine-rich domain therefore can be a molecular target in the development of an anti-Tat vaccine and agents for the control of extracellular-Tat-protein-mediated pathogenesis leading to the progression of acquired immunodeficiency syndrome.
authors.affiliation: Department of Pharmaceutical Biochemistry, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Misumi
authors.forename: Nobutoki
authors.initials: N
authors.lastname: Takamune
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Ohtsubo
authors.forename: Kazuya
authors.initials: K
authors.lastname: Waniguchi
authors.forename: Shozo
authors.initials: S
authors.lastname: Shoji
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000276:immunology / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001665:Binding Sites; D002460:Cell Line; D003545:Cysteine; D015696:Gene Products, tat / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000472:pathogenicity*; D006367:HeLa Cells / Q000821:virology; D006801:Humans; D019169:Jurkat Cells / Q000821:virology; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000276:immunology; D015533:Transcriptional Activation / Q000187:drug effects; D015032:Zinc / Q000378:metabolism*; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D000911:Antibodies, Monoclonal; D015696:Gene Products, tat; D010455:Peptides; D054322:tat Gene Products, Human Immunodeficiency Virus; D015032:Zinc; D003545:Cysteine