PMID:9927737

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Citation

Connelly, JC, de Leau, ES and Leach, DR (1999) DNA cleavage and degradation by the SbcCD protein complex from Escherichia coli. Nucleic Acids Res. 27:1039-46

Abstract

The SbcCD protein is a member of a group of nucleases found in bacteriophage T4 and T5, eubacteria, archaebacteria, yeast, Drosophila, mouse and man. Evidence from electron microscopy has revealed a distinctive structure consisting of two globular domains linked by a long region of coiled coil, similar to that predicted for the members of the SMC family. That a nuclease should have such an unusual structure suggests that its mode of action may be complex. Here we show that the protein degrades duplex DNA in a 3'-->5' direction. This degradation releases products half the length of the original duplex suggesting simultaneous degradation from two duplex ends. This may provide a link to the unusual structure of the protein since our data are consistent with recognition and cleavage of DNA ends followed by 3'-->5' nicking by two nucleolytic centres within a single nuclease molecule that releases a half length limit product. We also show that cleavage is not simply at the point of a single-strand/double-stand transition and that despite the dominant 3'-->5' polarity of degradation, a 5' single-strand can be cleaved when attached to duplex DNA. The implications of this mechanism for the processing of hairpins formed during DNA replication are discussed.

Links

PubMed PMC148284

Keywords

Bacterial Proteins/metabolism; Base Sequence; DNA/metabolism; DNA, Single-Stranded/metabolism; Deoxyribonucleases/metabolism; Endodeoxyribonucleases/metabolism; Escherichia coli/enzymology; Escherichia coli Proteins; Exodeoxyribonucleases/metabolism; Exonucleases/metabolism; Molecular Sequence Data; Oligodeoxyribonucleotides/metabolism; Structure-Activity Relationship

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