Kovall R A, Matthews B W
Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, University of Oregon, Eugene, OR 97403, USA.
Proc Natl Acad Sci U S A. 1998 Jul 7;95(14):7893-7. doi: 10.1073/pnas.95.14.7893.
lambda-exonuclease participates in DNA recombination and repair. It binds a free end of double-stranded DNA and degrades one strand in the 5' to 3' direction. The primary sequence does not appear to be related to any other protein, but the crystal structure shows part of lambda-exonuclease to be similar to the type II restriction endonucleases PvuII and EcoRV. There is also a weaker correspondence with EcoRI, BamHI, and Cfr10I. The structure comparisons not only suggest that these enzymes all share a similar catalytic mechanism and a common structural ancestor but also provide strong evidence that the toroidal structure of lambda-exonuclease encircles its DNA substrate during hydrolysis.
λ核酸外切酶参与DNA重组和修复。它结合双链DNA的一个自由末端，并沿5'至3'方向降解一条链。其一级序列似乎与任何其他蛋白质都无关，但晶体结构显示λ核酸外切酶的一部分与II型限制性内切酶PvuII和EcoRV相似。与EcoRI、BamHI和Cfr10I也有较弱的对应关系。结构比较不仅表明这些酶都共享相似的催化机制和共同的结构祖先，还提供了有力证据，证明λ核酸外切酶的环形结构在水解过程中环绕其DNA底物。
