Mobility of secondary structure units of horse-muscle acylphosphatase. Relation to antigenicity

The antigenic properties of acylphosphatase are compared with its various sequential characteristics (hydrophobicity, chemical shift of the main-chain 1H-NMR resonances, numbers and intensities of the nuclear Overhauser enhancements, hydrogen-deuterium exchange and sequential arrangement of the secondary structure units). The discussion is based on the complete sequential assignment of the 1H-NMR spectrum and the knowledge of the three-dimensional fold of the protein obtained by NMR spectroscopy from distance geometry calculations. Regions with very different degrees of mobility can be distinguished. It is found that all major antigenic sites are located in the most mobile surface loops.