A combinatorial disulfide cross-linking strategy was used to prepare a stalled complex of human immunodeficiency virus-type 1 (HIV-1) reverse transcriptase with a DNA template:primer and a deoxynucleoside triphosphate (dNTP), and the crystal structure of the complex was determined at a resolution of 3.2 angstroms. The presence of a dideoxynucleotide at the 3'-primer terminus allows capture of a state in which the substrates are poised for attack on the dNTP. Conformational changes that accompany formation of the catalytic complex produce distinct clusters of the residues that are altered in viruses resistant to nucleoside analog drugs. The positioning of these residues in the neighborhood of the dNTP helps to resolve some long-standing puzzles about the molecular basis of resistance. The resistance mutations are likely to influence binding or reactivity of the inhibitors, relative to normal dNTPs, and the clustering of the mutations correlates with the chemical structure of the drug.

BCL-2 family proteins constitute a critical control point for the regulation of apoptosis. Protein interaction between BCL-2 members is a prominent mechanism of control and is mediated through the amphipathic alpha-helical BH3 segment, an essential death domain. We used a chemical strategy, termed hydrocarbon stapling, to generate BH3 peptides with improved pharmacologic properties. The stapled peptides, called "stabilized alpha-helix of BCL-2 domains" (SAHBs), proved to be helical, protease-resistant, and cell-permeable molecules that bound with increased affinity to multidomain BCL-2 member pockets. A SAHB of the BH3 domain from the BID protein specifically activated the apoptotic pathway to kill leukemia cells. In addition, SAHB effectively inhibited the growth of human leukemia xenografts in vivo. Hydrocarbon stapling of native peptides may provide a useful strategy for experimental and therapeutic modulation of protein-protein interactions in many signaling pathways.

Spontaneous oxidation of guanine residues in DNA generates 8-oxoguanine (oxoG). By mispairing with adenine during replication, oxoG gives rise to a G x C --> T x A transversion, a frequent somatic mutation in human cancers. The dedicated repair pathway for oxoG centres on 8-oxoguanine DNA glycosylase (hOGG1), an enzyme that recognizes oxoG x C base pairs, catalysing expulsion of the oxoG and cleavage of the DNA backbone. Here we report the X-ray structure of the catalytic core of hOGG1 bound to oxoG x C-containing DNA at 2.1 A resolution. The structure reveals the mechanistic basis for the recognition and catalytic excision of DNA damage by hOGG1 and by other members of the enzyme superfamily to which it belongs. The structure also provides a rationale for the biochemical effects of inactivating mutations and polymorphisms in hOGG1. One known mutation, R154H, converts hOGG1 to a promutator by relaxing the specificity of the enzyme for the base opposite oxoG.