The 2.0 angstrom structure of the second calponin homology domain from theactin-binding region of the dystrophin homologue utrophin

Utrophin is a close homologue of dystrophin, the protein defective in Duche nne muscular dystrophy. Like dystrophin, it is composed of three regions: a n N-terminal region that binds actin filaments, a large central region with triple coiled-coil repeats, and a C-terminal region that interacts with co mponents in the dystroglycan protein complex at the plasma membrane. The N- terminal actin-binding region consists of two calponin homology domains and is related to the actin-binding domains of a superfamily of proteins inclu ding alpha-actinin, spectrin and fimbrin. Here, we present the 2.0 Angstrom structure of the second calponin homology domain of utrophin solved by X-r ay crystallography, and compare it to the other calponin homology domains p reviously determined from spectrin and fimbrin. (C) 1999 Academic Press.