HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bhaduri, T. Articles by Nagaraja, V. Search for Related Content PubMed PubMed Citation Articles by Bhaduri, T. Articles by Nagaraja, V. Social Bookmarking                      What's this?

J Biol Chem, Vol. 273, Issue 22, 13925-13932, May 29, 1998

DNA Topoisomerase I from Mycobacterium smegmatis
AN ENZYME WITH DISTINCT FEATURES

From the Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India

A type I topoisomerase has been purified to homogeneity from Mycobacterium smegmatis. It is the largest single subunit enzyme of this class having molecular mass of 110 kDa. The enzyme is Mg²⁺ dependent and can relax negatively supercoiled DNA, catenate, and knot single-stranded DNA, thus having typical properties of type I topoisomerases. Furthermore, the enzyme makes single-stranded nicks and the 5'-phosphoryl end of the nicked DNA gets covalently linked with a tyrosine residue of the enzyme. However, M. smegmatis enzyme shows some distinctive features from the prototype Escherichia coli topoisomerase I. The enzyme is relatively stable at higher temperatures and not inhibited by spermidine. It apparently does not contain any bound Zn²⁺ and on modification of cysteine residues retains the activity, suggesting the absence of the zinc-finger motif in DNA binding. Partially purified Mycobacterium tuberculosis topoisomerase I exhibits very similar properties with respect to size, stability, and reaction characteristics. Sequence comparison of topoisomerase I from E. coli and M. tuberculosis shows the absence of zinc-finger motifs in mycobacterial enzyme. Using a two-substrate assay system, we demonstrate that the enzyme acts processively at low ionic strength and switches over to distributive mode at high Mg²⁺ concentration. Significantly, the enzyme activity is stimulated by single strand DNA-binding protein. There is a potential to exploit the characteristics of the enzyme to develop it as a molecular target against mycobacterial infections.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				P. Dai, Y. Wang, R. Ye, L. Chen, and L. Huang DNA Topoisomerase III from the Hyperthermophilic Archaeon Sulfolobus solfataricus with Specific DNA Cleavage Activity J. Bacteriol., September 15, 2003; 185(18): 5500 - 5507. [Abstract] [Full Text] [PDF]

				M. Ashiuchi, E. Kuwana, T. Yamamoto, K. Komatsu, K. Soda, and H. Misono Glutamate Racemase Is an Endogenous DNA Gyrase Inhibitor J. Biol. Chem., October 11, 2002; 277(42): 39070 - 39073. [Abstract] [Full Text] [PDF]

				D. Sikder and V. Nagaraja Determination of the recognition sequence of Mycobacterium smegmatis topoisomerase I on mycobacterial genomic sequences Nucleic Acids Res., April 15, 2000; 28(8): 1830 - 1837. [Abstract] [Full Text] [PDF]