CEM15/APOBEC3G is a cellular protein required for resistance to infection by virion infectivity factor (Vif)-deficient human immunodeficiency virus (HIV). Here, using a murine leukemia virus (MLV)-based system, we provide evidence that CEM15/APOBEC3G is a DNA deaminase that is incorporated into virions during viral production and subsequently triggers massive deamination of deoxycytidine to deoxyuridine within the retroviral minus (first)-strand cDNA, thus providing a probable trigger for viral destruction. Furthermore, HIV Vif can protect MLV from this CEM15/APOBEC3G-dependent restriction. These findings imply that targeted DNA deamination is a major strategy of innate immunity to retroviruses and likely also contributes to the sequence variation observed in many viruses (including HIV).

The May 28, 2003 immediate early online version of this article (Cell 113, 803-809, 13 June 2003) contained one sentence that did not appear in the printed version. In the results subsection entitled "CEM15/APOBEC3G Is Incorporated into MLV Virions," a bracketed sentence appeared in the following context: The CEM15/APOBEC3G-mediated suppression of HIV infection is thought to be accomplished by protein transferred as a virion component from virus producing cells into target cells (curiously, such physical transfer of CEM15/ APOBEC3G appears uninhibitable by Vif) (Sheehy et al., 2002). The bracketed text was removed prior to publication of the definitive printed and corresponding online versions of the manuscript. It was our intention that this correction should have occurred in all versions of the article. The authors and Cell Press apologize for any inconvenience that may have been caused.

The catalytic domain of the F-ATPase in mitochondria protrudes into the matrix of the organelle, and is attached to the membrane domain by central and peripheral stalks. Energy for the synthesis of ATP from ADP and phosphate is provided by the transmembrane proton-motive-force across the inner membrane, generated by respiration. The proton-motive force is coupled mechanically to ATP synthesis by the rotation at about 100 times per second of the central stalk and an attached ring of c-subunits in the membrane domain. Each c-subunit carries a glutamate exposed around the midpoint of the membrane on the external surface of the ring. The rotation is generated by protonation and deprotonation successively of each glutamate. Each 360°rotation produces three ATP molecules, and requires the translocation of one proton per glutamate by each c-subunit in the ring. In fungi, eubacteria, and plant chloroplasts, ring sizes of c 10