title: Single-stranded regions in transforming deoxyribonucleic acid after uptake by competent Haemophilus influenzae.
abstract: About 15% of donor deoxyribonucleic acid (DNA) is single stranded immediately after uptake into competent Haemophilus influenzae wild-type cells, as judged by its sensitivity to S1 endonuclease. This amount decreases to 4 to 5% by 30 min after uptake. Mutants which are defective in the covalent association of recipient and donor DNA form little or no S1 endonuclease-sensitive donor. At 17 C donor DNA taken up by the wild type contains single-stranded regions although there is no observable association, either covalent or noncovalent. The single-stranded regions are at the ends of donor DNA molecules, as judged by the unchanged sedimentation velocity after S1 endonuclease digestion. The amount of single-stranded donor remains constant at 17 C for more than 60 min after uptake, suggesting that the decrease observed at 37 C is the result of association of single-stranded ends with single-stranded regions of recipient cell DNA. Three sequential steps necessary for the integration of donor DNA into recipient DNA are proposed: the synthesis of single-stranded regions in recipient DNA, the interaction of donor DNA with recipient DNA resulting in the production of single-stranded ends on donor DNA, and the stable pairing of homologous single-stranded regions.
mesh_terms: D004269:DNA, Bacterial / Q000032:analysis* / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000032:analysis* / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism; D006193:Haemophilus influenzae / Q000032:analysis* / Q000378:metabolism; D009154:Mutation; D013696:Temperature; D014170:Transformation, Genetic
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004720:Endonucleases