Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA cytosine methyltransferase MspI (M.MspI) must require a different type of interaction of protein with DNA from other bacterial DNA cytosine methyltransferases (m5C-MTases) to evoke the topoisomerase activity that it possesses in addition to DNA-methylation ability. This may require a different structural organization in the solution phase from the reported consensus structural arrangement for m5C-MTases. Limited proteolysis of M.MspI, however, generates two peptide fragments, a large one (p26) and a small one (p18), consistent with reported m5C-MTase structures. Examination of the amino-acid sequence of M.MspI revealed similarity to human topoisomerase I at the N-terminus. Alignment of the amino-acid sequence of M.MspI also uncovered similarity (residues 245-287) to the active site of human DNA ligase I. To evaluate the role of the N-terminus of M.MspI, 2-hydroxy-5-nitrobenzyl bromide (HNBB) was used to truncate M.MspI between residues 34 and 35. The purified HNBB-truncated protein has a molecular mass of approximately equal 45 kDa, retains DNA binding and methyltransferase activity, but does not possess topoisomerase activity. These findings were substantiated using a purified recombinant MspI protein with the N-terminal 34 amino acids deleted. Changing the N-terminal residues Trp34 and Tyr74 to alanine results in abolition of the topoisomerase I activity while the methyltransferase activity remains intact.
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PMID:The N-terminus of m5C-DNA methyltransferase MspI is involved in its topoisomerase activity. 1202 87

A peptide fragment (p26) generated as a result of limited tryptic proteolysis of methyltransferase MspI retains transient but non-specific DNA binding capability. The transient DNA binding by p26 was characterized with respect to physicochemical factors. Limited proteolysis was performed to probe gross structural deviation from the reported two-domain organization for m5C-MTases, in light of topoisomerase activity shown by MspI, resulted in two peptide fragments; a large fragment p26 and a small fragment p18, consistent with the other reported m5C-MTase structures. The purified large peptide fragment p26, spans between 6 and 251 in the amino acid sequence of M.MspI. The peptide p26 does not bind S-adenosylmethionine, although in the intact protein the AdoMet binding region can be mapped to a region in the protein that is present in this peptide. Such transient DNA binding has not been reported for other protolytic product of any other m5C-DNA methyltransferase.
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PMID:Transient DNA binding by a proteolytic peptide from m5C-DNA methyltransferase MspI. 1238 73