Crystallisation and characterisation of muscle proteins: a mini-review

Abstract

The techniques of X-ray protein crystallography, NMR and high-resolution cryo-electron microscopy have all been used to determine the high-resolution structure of proteins. The most-commonly used method, however, remains X-ray diffraction but it does rely heavily on the production of suitable crystals. Indeed, the production of diffraction quality crystals remains the rate-limiting step for most protein systems. Crystallisation trials, initiated by John Squire with the assistance of the authors, used existing and newly developed crystallisation methods for two different muscle proteins - the actin binding domain (ABD) of α-actinin and the C0-C1 domain of human cardiac myosin binding protein C (cMyBP-C). Diffracting crystals of α-actinin ABD, with a resolution of 1.9Å, however, did not prove to be in a form suitable for diffraction methods. In contrast, when the C0-C1 domain of cMyBP-C underwent proteolysis during crystallogenesis very satisfactory crystals of the C1 domain were obtained. These employed a modified hanging drop vapour diffusion method and diffracted to high resolution (1.5Å). This has led to the determination of the structure of the C1 domain of cMyBP-C at atomic resolution and has thereby provided new insights into its function.