Guo F, Gopaul D N, van Duyne G D
Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
Nature. 1997 Sep 4;389(6646):40-6. doi: 10.1038/37925.
During site-specific DNA recombination, which brings about genetic rearrangement in processes such as viral integration and excision and chromosomal segregation, recombinase enzymes recognize specific DNA sequences and catalyse the reciprocal exchange of DNA strands between these sites. The bacteriophage recombinase Cre catalyses site-specific recombination between two 34-base-pair loxP sites. The crystal structure at 2.4 A resolution of Cre bound to a loxP substrate reveals an intermediate in the recombination reaction, in which a Cre molecule has cleaved the substrate to form a covalent 3'-phosphotyrosine linkage with the DNA. Four recombinases and two loxP sites form a synapsed structure in which the DNA resembles models of four-way Holliday-Junction intermediates. The Cre-loxP complex challenges models of site-specific recombination that require large changes in quaternary structure. Subtle allosteric changes at the carboxy termini of the Cre subunits may instead coordinate the cleavage and strand-exchange reactions.
在位点特异性DNA重组过程中，会在病毒整合与切除以及染色体分离等过程中引发基因重排，重组酶能够识别特定的DNA序列，并催化这些位点之间DNA链的相互交换。噬菌体重组酶Cre催化两个34碱基对的loxP位点之间的位点特异性重组。Cre与loxP底物结合的2.4埃分辨率晶体结构揭示了重组反应中的一个中间体，其中一个Cre分子已切割底物，与DNA形成共价3'-磷酸酪氨酸连接。四个重组酶和两个loxP位点形成一个联会结构，其中DNA类似于四向霍利迪连接中间体模型。Cre-loxP复合物对需要四级结构发生重大变化的位点特异性重组模型提出了挑战。相反，Cre亚基羧基末端的微妙变构变化可能会协调切割和链交换反应。
