Enzyme proteins frequently combine to form multimeric complexes that allow individual subunits to coordinate their activities and so perform more difficult tasks than they could alone. An example of such a complex is the ring ATPases in which several subunits form circular complexes consisting of identical (homomeric) or non-identical (heteromeric) subunits. These enzyme complexes use energy released from the hydrolysis of ATP molecules to perform diverse cellular functions, such as DNA translocation, protein degradation and ion transport.
Subunits of the various ring ATPases can coordinate their activities in different ways. For instance, the three heterodimers of the Fl- ATPase act sequentially, each binding an ATP molecule and hydrolysing it in order. By contrast, subunits of the L Tag helicase of simian virus 40 seem to act in concert, all six of them simultaneously binding then hydrolysing ATP molecules. Subunits of the unfoldase enzyme ClpX, however, are thought to act randomly, each one hydrolysing ATP independently, with their activities probably being coordinated by the geometry of the complex.
Abbondanzieri and Zhuang 2009 Concealed enzyme co-coordination Nature vol 457 pp 392 – 3
- Martin Eastwood