6pcm

Structural highlights

Function

[TOP1_MYCS2] Releases the supercoiling and torsional tension of DNA, which is introduced during the DNA replication and transcription, by transiently cleaving and rejoining one strand of the DNA duplex. Introduces a single-strand break via transesterification at a target site in duplex DNA. The scissile phosphodiester is attacked by the catalytic tyrosine of the enzyme, resulting in the formation of a DNA-(5'-phosphotyrosyl)-enzyme intermediate (PubMed:9593741) and the expulsion of a 3'-OH DNA strand. The free DNA strand then undergoes passage around the unbroken strand, thus removing DNA supercoils. Finally, in the religation step, the DNA 3'-OH attacks the covalent intermediate to expel the active-site tyrosine and restore the DNA phosphodiester backbone (By similarity).[HAMAP-Rule:MF_00952]^[1] Relaxes negatively (but not positively) supercoiled DNA, concatanates and knots circular ssDNA at 52 but not 37 degrees Celsius (PubMed:9593741). Preferentially nicks supercoiled DNA at C(G/T)CTT, cutting between the TT residues, binds ss and dsDNA with the recognition site (PubMed:10734203).^{[2] [3]}

References

1. ↑ Bhaduri T, Bagui TK, Sikder D, Nagaraja V. DNA topoisomerase I from Mycobacterium smegmatis. An enzyme with distinct features. J Biol Chem. 1998 May 29;273(22):13925-32. doi: 10.1074/jbc.273.22.13925. PMID:9593741 doi:http://dx.doi.org/10.1074/jbc.273.22.13925
2. ↑ Sikder D, Nagaraja V. Determination of the recognition sequence of Mycobacterium smegmatis topoisomerase I on mycobacterial genomic sequences. Nucleic Acids Res. 2000 Apr 15;28(8):1830-7. doi: 10.1093/nar/28.8.1830. PMID:10734203 doi:http://dx.doi.org/10.1093/nar/28.8.1830
3. ↑ Bhaduri T, Bagui TK, Sikder D, Nagaraja V. DNA topoisomerase I from Mycobacterium smegmatis. An enzyme with distinct features. J Biol Chem. 1998 May 29;273(22):13925-32. doi: 10.1074/jbc.273.22.13925. PMID:9593741 doi:http://dx.doi.org/10.1074/jbc.273.22.13925