tailieunhanh - báo cáo khoa hoc : DNA binding activity of Helicobacter pylori DnaB helicase: the role of the N-terminal domain in modulating DNA binding activities

Replicative helicases are major motor proteins essential for chromosomal DNA replication in prokaryotes. Usually hexameric in solution, their DNA binding property must have different roles at stages ranging from the load-ing onto a branched structure at initiation from the origin to the highly pro-cessive translocation during elongation. | IFEBS Journal DNA binding activity of Helicobacter pylori DnaB helicase the role of the N-terminal domain in modulating DNA binding activities Ram G. Nitharwal1 Vijay Verma1 Naidu Subbarao2 Santanu Dasgupta3 Nirupam R. Choudhury4 and Suman K. Dhar1 1 SpecialCentre for Molecular Medicine JawaharlalNehru University New Delhi India 2 Schoolof Computationaland Integrative Sciences JawaharlalNehru University New Delhi India 3 Department of Celland Molecular Biology Uppsala University Sweden 4 InternationalCentre for Genetic Engineering and Biotechnology New Delhi India Keywords DNA binding DNA replication DnaB helicase Helicobacter pylori ssDNA Correspondence Suman K. Dhar Special Centre for Molecular Medicine JawaharlalNehru University New Delhi 110067 India Fax 91 11 2674 1781 Tel 91 11 2674 2572 E-mail skdhar2002@ Nirupam Roy Choudhury International Centre for Genetic Engineering and Biotechnology Aruna Asaf Ali Marg New Delhi 110067 India Fax 91 11 2674 2316 Tel 91 11 2674 1358 E-mail nirupam@ Contributed equally to this work Received 19 July 2011 revised 5 October 2011 accepted 26 October 2011 doi Replicative helicases are major motor proteins essential for chromosomal DNA replication in prokaryotes. Usually hexameric in solution their DNA binding property must have different roles at stages ranging from the loading onto a branched structure at initiation from the origin to the highly pro-cessive translocation during elongation. Here we have analysed the DNA binding activity of Helicobacter pylori Hp replicative helicase DnaB. The results indicate that while the C-terminal region is important for its DNA binding activity the N-terminus appears to dampen the protein s affinity for DNA. The masking activity of the N-terminus does not require ATP or hexamerization of HpDnaB and can be overcome by deleting the N-termi-nus. It can also be neutralized by engaging the N-terminus in an interaction with a partner like