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EMBO J. 2000 Jun 15;19(12):3110-8.

Crystal structure of NaeI-an evolutionary bridge between DNA endonuclease and topoisomerase.

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Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, The University of North Carolina, Chapel Hill, NC 27599-7260, USA.


NAE:I is transformed from DNA endonuclease to DNA topoisomerase and recombinase by a single amino acid substitution. The crystal structure of NAE:I was solved at 2.3 A resolution and shows that NAE:I is a dimeric molecule with two domains per monomer. Each domain contains one potential DNA recognition motif corresponding to either endonuclease or topoisomerase activity. The N-terminal domain core folds like the other type II restriction endonucleases as well as lambda-exonuclease and the DNA repair enzymes MutH and Vsr, implying a common evolutionary origin and catalytic mechanism. The C-terminal domain contains a catabolite activator protein (CAP) motif present in many DNA-binding proteins, including the type IA and type II topoisomerases. Thus, the NAE:I structure implies that DNA processing enzymes evolved from a few common ancestors. NAE:I may be an evolutionary bridge between endonuclease and DNA processing enzymes.

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