Single-stranded DNA Scanning and Deamination by APOBEC3G Cytidine Deaminase at Single Molecule Resolution

摘要: APOBEC3G (Apo3G) is a single-stranded (ss)DNA cytosine deaminase that eliminates HIV-1 infectivity by converting C → U in numerous small target motifs on the minus viral cDNA. Apo3G deaminates linear ssDNA vitro with pronounced spatial asymmetry favoring 3′ 5′ direction. A similar polarity observed vivo believed responsible for initiating localized T mutational gradients inactivate virus. When compared double-stranded (ds)DNA scanning enzymes, e.g. DNA glycosylases excise rare aberrant bases, there paucity of mechanistic studies enzymes. Here, we investigate and motif-targeting mechanisms using single molecule Forster resonance energy transfer. We address specific issue deamination within general context show trajectories, contraction, efficiencies depend motif sequence, location, ionic strength. Notably, observe presence bidirectional quasi-localized occurring proximal to hot motif, motif-dependent contraction greatest > cold motifs, diminished mobility at low salt. discuss transfer data terms model which occurs as consequence binding two orientations, one catalytically favorable, other disfavorable.