H. volcanii MSH oligomerization. a) A trimeric assembly rendered as cartoon ribbon traces, viewed along a crystallographic 3-fold rotation axis. Acetyl-coenzyme A and pyruvate are shown as space-filling models in slate blue and orange respectively. b) A hexameric assembly viewed along a crystallographic 2-fold rotation axis, perpendicular to the view in part a. The top trimer is rendered and colored as in part a.