复制第二讲.ppt

免疫学信息网 * Looping the lagging strand to make both polymerases move in the same direction The discovery of DNA polymerase. Arthur Kornberg and Bob Lehman pursued an enzyme in bacterial extracts that would elongate a chain of deoxyribonucleic acid just like glycogen synthase elongates a chain of glycogen. The enzymatic activity was unusual: 1) Needed a template which dictates what nucleotide was added: substrate was directing enzymatic activity 2) Needed a primer annealed to the template. Wait a minute! John Cairns mutated the gene for DNA polymerase, polA, and the bacteria grew just fine! Either the polymerase hypothesis was all wrong,…… or there were other DNA polymerases in E. coli that carried out DNA synthesis in the polA strains. Which polymerase is processive? POLIII, b subunit PCNA Clamp loaders hydrolyze ATP to load clamp How does one prove that the clamp ring is opened during loading? 免疫学信息网 *