The domain organization of NaeI endonuclease: Separation of binding and catalysis
AUTOR(ES)
Colandene, James D.
FONTE
The National Academy of Sciences
RESUMO
NaeI is a remarkable type II restriction endonuclease. It must bind two recognition sequences to cleave DNA, forms a covalent protein–DNA intermediate, and is only 1 aa change away from topoisomerase and recombinase activity. The latter activities apparently derive from reactivation of a cryptic DNA ligase active site. Here, we demonstrate that NaeI has two protease-resistant domains, involving approximately the N-terminal and C-terminal halves of the protein, linked by a protease-accessible region of 30 aa. The domains were purified by cloning. The C-terminal domain was shown by gel mobility-shift assay to have approximately 8-fold lower DNA-binding ability than intact NaeI. Analytical ultracentrifugation showed this domain to be a monomer in solution. The N-terminal domain, which contains the catalytic region defined by random mutagenesis, did not bind DNA and was a mixture of different-sized complexes in solution implying that it mediates self-association. DNA greatly inhibited proteolysis of the linker region. The results identify the DNA-binding domain, imply that DNA cleavage and recognition are independent and separable, and lead us to speculate about a cleft-like structure for NaeI.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=19870Documentos Relacionados
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