‘LeishMan’ Topoisomerase I: an Ideal Chimera for Unraveling the Role of the Small Subunit of Unusual bi-subunit Topoisomerase I from Leishmania donovani

Ganguly, Agneyo and Das, Benu Brata and Sen, Nilkantha and Roy, Amit and Bose Dasgupta, Somdeb and Majumder, Hemanta K (2006) ‘LeishMan’ Topoisomerase I: an Ideal Chimera for Unraveling the Role of the Small Subunit of Unusual bi-subunit Topoisomerase I from Leishmania donovani. Nucleic Acids Research, 34 (21). pp. 6286-6297.

[img]

PDF
Restricted to IICB Scientists only

Download (1672Kb) | Request a copy

    Abstract

    The active site tyrosine residue of all monomeric type IB topoisomerases resides in the C-terminal domain of the enzyme. Leishmania donovani, possesses unusual heterodimeric type IB topoisomerase. The small subunit harbors the catalytic tyrosine within the SKXXY motif. To explore the functional relationship between the two subunits, we have replaced the small subunit of L.donovani topoisomerase I with a C-terminal fragment of human topoisomerase I (HTOP14). The purified LdTOP1L (large subunit of L.donovani topoisomerase I) and HTOP14 were able to reconstitute topoisomerase I activity when mixed in vitro. This unusual enzyme, ‘LeishMan’ topoisomerase I (Leish for Leishmania and Man for human) exhibits less efficiency in DNA binding and strand passage compared with LdTOP1L/S. Fusion of LdTOP1L with HTOP14 yielded a more efficient enzyme with greater affinity for DNA and faster strand passage ability. Both the chimeric enzymes are less sensitive to camptothecin than LdTOP1L/S. Restoration of topoisomerase I activity by LdTOP1L and HTOP14 suggests that the small subunit of L.donovani topoisomerase I is primarily required for supplying the catalytic tyrosine. Moreover, changes in the enzyme properties due to substitution of LdTOP1S with HTOP14 indicate that the small subunit contributes to subunit interaction and catalytic efficiency of the enzyme

    Item Type: Article
    URI: http://www.eprints.iicb.res.in/id/eprint/438
    Subjects: Infectious Diseases and Immunology
    Divisions: Indian Institute of Chemical Biology
    Depositing User: Ms Sutapa Ganguly
    Date Deposited: 01 Nov 2011 14:52
    Last Modified: 27 Jan 2012 14:54
    Official URL: http://dx.doi.org/10.1093/nar/gkl829
    Links:

    Actions (login required)

    View Item