An open or closed case for the conformation of calponin homology domains on F-actin?

Calponin homology domains link many different proteins to the surface of actin filaments. However, details of the structural interactions involved and the methods used to determine them are controversial. In the case of the actin-binding protein utrophin, for example, several models have been proposed for the binding of utrophin's calponin homology domains to actin. We review and evaluate these models and their supporting data.