Published online 5 March 2004
Nucleic Acids Research, 2004, Vol. 32, No. 4 1548-1554
© 2004 Oxford University Press
Interaction of human and bacterial AlkB proteins with DNA as probed through chemical cross-linking studies
Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA
*To whom correspondence should be addressed. Tel: +1 773 7025061; Fax: +1 773 7020805; Email: chuanhe{at}uchicago.edu
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors
The Escherichia coli AlkB protein was recently found to repair cytotoxic DNA lesions 1-methyladenine and 3-methylcytosine by using a novel iron-catalyzed oxidative demethylation mechanism. Three human homologs, ABH1, ABH2 and ABH3, have been identified, and two of them, ABH2 and ABH3, were shown to have similar repair activities to E.coli AlkB. However, ABH1 did not show any repair activity. It was suggested that ABH3 prefers single-stranded DNA and RNA substrates, whereas AlkB and ABH2 can repair damage in both single- and double-stranded DNA. We employed a chemical cross-linking approach to probe the structure and substrate preferences of AlkB and its three human homologs. The putative active site iron ligands in these proteins were mutated to cysteine residues. These mutant proteins were used to cross-link to different DNA probes bearing thiol-tethered bases. Disulfide-linked proteinDNA complexes can be trapped and analyzed by SDSPAGE. Our results show that ABH2 and ABH3 have structural and functional similarities to E.coli AlkB. ABH3 shows preference for the single-stranded DNA probe. ABH1 failed to cross-link to the probes tested. This protein, unlike other AlkB proteins, does not seem to interact with DNA in its E.coli expressed form.
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