title: Structural model for deoxycytidine deamination mechanisms of the HIV-1 inactivation enzyme APOBEC3G.
abstract: APOBEC3G (Apo3G) is a single-stranded DNA-dependent deoxycytidine deaminase, which, in the absence of the human immunodeficiency virus (HIV) viral infectivity factor, is encapsulated into HIV virions. Subsequently, Apo3G triggers viral inactivation by processively deaminating C-->U, with 3'-->5' polarity, on nascent minus-strand cDNA. Apo3G has a catalytically inactive N-terminal CD1 domain and an active C-terminal CD2 domain. Apo3G exists as monomers, dimers, tetramers, and higher order oligomers whose distributions depend on DNA substrate and salt. Here we use multiangle light scattering and atomic force microscopy to identify oligomerization states of Apo3G. A double mutant (F126A/W127A), designed to disrupt dimerization at the predicted CD1-CD1 dimer interface, predominantly converts Apo3G to a monomer that binds single-stranded DNA, Alu RNA, and catalyzes processive C-->U deaminations with 3'-->5' deamination polarity, similar to native Apo3G. The CD1 domain is essential for both processivity and polarity. We propose a structure-based model to explain the scanning and catalytic behavior of Apo3G.
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2910, USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Chelico
authors.forename: Courtney
authors.initials: C
authors.lastname: Prochnow
authors.forename: Dorothy A
authors.initials: DA
authors.lastname: Erie
authors.forename: Xiaojiang S
authors.initials: XS
authors.lastname: Chen
authors.forename: Myron F
authors.initials: MF
authors.lastname: Goodman
mesh_terms: D000071480:APOBEC-3G Deaminase; D020087:Alu Elements; D003564:Cytidine Deaminase / Q000737:chemistry* / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry* / Q000378:metabolism; D003641:Deamination; D015497:HIV-1; D006801:Humans; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship; D014771:Virion
chemical_list: D018076:DNA, Complementary; D012313:RNA; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; D003564:Cytidine Deaminase