Characterization of the mycobacterial chromosome segregation protein ParB and identification of its target in Mycobacterium smegmatis

1 Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, ul. Weigla 12, 53-114 Wroc aw, Poland 2 Faculty of Biotechnology, University of Wroclaw, ul. Tamka 2, 50-137 Wroclaw, Poland 3 Medical Biology Center, Polish Academy of Sciences, Lodowa 106, 93-232 ód , Poland Correspondence Jolanta Zakrzewska-Czerwi ska zakrzew{at}iitd.pan.wroc.pl Bacterial chromosomes (though not Escherichia coli and some other -proteobacterial chromosomes) contain parS sequences and parAB genes encoding partitioning proteins, i.e. ParA (ATPase) and ParB (DNA-binding proteins) that are components of the segregation machinery. Here, mycobacterial parABS elements were characterized for the first time. parAB genes are not essential in Mycobacterium smegmatis; however, elimination or overexpression of ParB protein causes growth inhibition. Deletion of parB also leads to a rather severe chromosome segregation defect: up to 10 % of the cells were anucleate. Mycobacterial ParB protein uses three oriC -proximal parS sequences as targets to organize the origin region into a compact nucleoprotein complex. Formation of such a complex involves ParB–ParB interactions and is assisted by ParA protein. Abbreviations: EMSA, electrophoretic mobility shift assay; GST, glutathione S -transferase; Ms , M. smegmatis ; Mt , M. tuberculosis Three supplementary figures showing the construction of the M. smegmatis parB mutant, purified mycobacterial ParAB proteins and protein sequence alignment of homologous ParB proteins, and a supplementary table listing the oligonucleotides used in this study are available with the online version of this paper.