Abstract:
:Kinetoplastid topoisomerase IB is an unusual bisubunit enzyme where reconstitution of the large (LdTOPIL or L) and small (LdTOPIS or S) subunits shows functional activity. It is yet to be deciphered whether one subunit or both navigate the heterodimer to its cellular DNA targets. Tethering a specific DNA-binding protein to topoisomerase I alters its site specificity. The chimeric constructs UMSBP-LdTOPIL/S or U-L/S (fusion of UMSBP to the N-terminus of L and reconstituted with S) and LdTOPIL/UMSBP-LdTOPIS or L/U-S (fusion of UMSBP to the N-terminus of S and reconstituted with L) exhibit relaxation activity. Only U-L/S shows altered site specificity and enhanced DNA-binding affinity for the universal minicircle sequence (UMS) containing substrate. This proves that L alone serves as the 'molecular steer' for this heterodimer. Reconstituted U-L/S also induces cleavage close to UMS and causes minicircle linearization. The differential properties of the reconstituted chimeras U-L/S and L/U-S reveal the structural and functional asymmetry between the heterodimer. Therefore this study helps in a better understanding of the mechanistic details underlying topoisomerization by this bi-subunit enzyme.
journal_name
Mol Microbioljournal_title
Molecular microbiologyauthors
BoseDasgupta S,Ganguly A,Das BB,Roy A,Khalkho NV,Majumder HKdoi
10.1111/j.1365-2958.2007.06002.xsubject
Has Abstractpub_date
2008-01-01 00:00:00pages
31-46issue
1eissn
0950-382Xissn
1365-2958pii
MMI6002journal_volume
67pub_type
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