Practice question

Type II partition system ParM ParR ParC extensively studied molecularly via electron microscopy and total internal reflection fluorescence revealing filaments pushing plasmids. parC centromere comprises two clusters five 11 base pair direct repeats separated binding ParR dimers forming helical clamp around DNA. ParR directly interacts with ParM filament ends increasing elongation rate. Filaments grow bipolarly inserting monomers at parC ParR junction producing pushing force separating plasmids by up to cell length. After plasmids reach poles ParM hydrolyzes ATP destabilizing filaments recycling monomers. While some literature loosely describes adaptor interactions with membrane, primary function not membrane anchoring but segregation ensuring each daughter inherits plasmid. System analogous to eukaryotic anaphase B spindle elongation. Mutations in ParM Walker A lysine abolish ATPase eliminate plasmid stability increasing loss rate thousand fold. Understanding ParM ParR ParC mechanism informs synthetic biology construction stable low copy vectors and insight how bacteria solve problem genome distribution without nuclear envelope and mitotic apparatus using cytoskeletal polymers.