Hacker K J, Alberts B M
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.
J Biol Chem. 1992 Oct 15;267(29):20674-81.
The bacteriophage T4 dda protein is a 5'-3' DNA helicase that stimulates DNA replication and recombination reactions in vitro and seems to play a role in the initiation of T4 DNA replication in vivo. Oligonucleotide probes based on NH2-terminal amino acid sequence were used to precisely map the location of the dda gene on the T4 chromosome. Using polymerase chain reaction techniques, the dda gene was then cloned into an expression vector, and the overproduced protein was purified in two chromatography steps. Both the genomic and cloned dda genes were sequenced and found to be identical, encoding a protein of 439 amino acids. The dda protein contains amino acid sequences resembling those of other known helicases, and is most homologous to the Escherichia coli recD protein. Protein affinity chromatography was used to show a direct interaction between the dda protein and the T4 uvsX protein (a rec A-type DNA recombinase).
噬菌体T4 dda蛋白是一种5'-3' DNA解旋酶，它在体外能刺激DNA复制和重组反应，且似乎在体内T4 DNA复制的起始过程中发挥作用。基于NH2末端氨基酸序列的寡核苷酸探针被用于精确绘制dda基因在T4染色体上的位置。利用聚合酶链反应技术，随后将dda基因克隆到一个表达载体中，并通过两步色谱法纯化过量表达的蛋白。对基因组dda基因和克隆的dda基因都进行了测序，发现二者相同，编码一个含有439个氨基酸的蛋白。dda蛋白含有与其他已知解旋酶相似的氨基酸序列，与大肠杆菌recD蛋白的同源性最高。利用蛋白亲和色谱法显示了dda蛋白与T4 uvsX蛋白（一种rec A型DNA重组酶）之间存在直接相互作用。
