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PDBsum entry 1gj2
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References listed in PDB file
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Key reference
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Title
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Solution structure of co(III)-Bleomycin-Ooh bound to a phosphoglycolate lesion containing oligonucleotide: implications for bleomycin-Induced double-Strand DNA cleavage.
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Authors
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S.T.Hoehn,
H.D.Junker,
R.C.Bunt,
C.J.Turner,
J.Stubbe.
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Ref.
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Biochemistry, 2001,
40,
5894-5905.
[DOI no: ]
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PubMed id
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Abstract
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Bleomycin (BLM) is an antitumor antibiotic that is used clinically. Its major
cause of cytotoxicity is thought to be related to BLM's ability to cause
double-strand (ds) DNA cleavage. A single molecule of BLM appears to cleave both
strands of DNA in the presence of its required cofactors Fe(2+) and oxygen
without dissociating from the helix. A mechanism for this process has been
proposed based on a model structure of the hydroperoxide of Co(III)-BLM (CoBLM)
bound sequence-specifically to an intact duplex containing a GTAC site, a hot
spot for ds cleavage [Vanderwall, D. E., Lui, S. M., Wu, W., Turner, C. J.,
Kozarich, J. W., and Stubbe, J. (1997) Chem. Biol. 4, 373-387]. In this paper,
we present a structural model for the second cleavage event. Two-dimensional NMR
spectroscopy and molecular modeling were carried out to study CoBLM bound to
d(CCAAAGXACTGGG).d(CCCAGTACTTTGG), where X represents a 3'-phosphoglycolate
lesion next to a 5'-phosphate. Assignments of 729 NOEs, including 51 between the
drug and the DNA and 126 within the BLM molecule, have been made. These NOEs in
addition to 96 dihedral angle constraints have been used to obtain a
well-defined structural model for this complex. The model reveals that the
bithiazole tail is partially intercalated between the T19 and the A20 of the
duplex and that the metal binding domain is poised for abstraction of the T19
H4' in the minor groove. The modeling further reveals that the predominant
conformation of the bithiazole protons is trans. Two cis conformations of these
protons are also observed, and ROESY experiments provide evidence for
interconversion of all of these forms. The relationship of these observations to
the model for ds cleavage is presented.
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Headers
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