| The Ku 70 autoantigen interacts with p40phox in B lymphocytes . ^^^ Ku 70 , a regulatory component of the DNA dependent protein kinase , was identified by a yeast two hybrid screen of a B lymphocyte cDNA library as a partner of p40phox , a regulatory component of the O 2 producing NADPH oxidase . ^^^ Truncated constructs of p40phox and Ku 70 were used to map the interacting sites . ^^^ The 186 C terminal amino acids ( aa ) of Ku 70 were found to interact with two distinct regions of p40phox , the central core region ( aa 50 260 ) and the C terminal extremity ( aa 260 339 ) . ^^^ In complementary experiments , it was observed that Ku 70 binds to immobilized recombinant p40phox fusion protein and that p40phox and Ku 70 from a B lymphocyte cell extract comigrate in successive chromatographies on Q Separose , Superose 12 and hydroxylapatite columns . ^^^ |