Kwon H J, Tirumalai R, Landy A, Ellenberger T
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston MA 02115, USA.
Science. 1997 Apr 4;276(5309):126-31. doi: 10.1126/science.276.5309.126.
Lambda integrase is archetypic of site-specific recombinases that catalyze intermolecular DNA rearrangements without energetic input. DNA cleavage, strand exchange, and religation steps are linked by a covalent phosphotyrosine intermediate in which Tyr342 is attached to the 3'-phosphate of the DNA cut site. The 1.9 angstrom crystal structure of the integrase catalytic domain reveals a protein fold that is conserved in organisms ranging from archaebacteria to yeast and that suggests a model for interaction with target DNA. The attacking Tyr342 nucleophile is located on a flexible loop about 20 angstroms from a basic groove that contains all the other catalytically essential residues. This bipartite active site can account for several apparently paradoxical features of integrase family recombinases, including the capacity for both cis and trans cleavage of DNA.
λ整合酶是位点特异性重组酶的典型代表,它能催化分子间DNA重排,且无需能量输入。DNA切割、链交换和重新连接步骤通过共价磷酸酪氨酸中间体相连,其中Tyr342连接到DNA切割位点的3'-磷酸上。整合酶催化结构域的1.9埃晶体结构揭示了一种在从古细菌到酵母的生物体中保守的蛋白质折叠,这暗示了一种与靶DNA相互作用的模型。具有攻击性的亲核体Tyr342位于一个柔性环上,距离一个包含所有其他催化必需残基的碱性凹槽约20埃。这种二分活性位点可以解释整合酶家族重组酶的几个明显矛盾的特征,包括DNA顺式和反式切割的能力。