Nebulin Related Anchoring Protein (NRAP)

Nebulin is a family of giant myofibrillar proteins found within the sarcomeres of skeletal muscle. Over 95% of the nebulin protein consists of 185 copies of a 35- to 40-amino acid module. Most of the modules are arranged into a higher order repeating sequence termed a """nebulin super repeat.""" Sequence analysis predicted that NRAP is a 1,175-amino acid protein with a pI of 9.26. The C-terminal half of NRAP includes an actin-binding domain with homology to the nebulin super repeats. The N-terminal region contains a LIM domain, thought to mediate protein-protein interactions. Northern blot analysis of various mouse tissues revealed that NRAP is expressed as a 6-kb mRNA only in skeletal muscle and heart. Antibodies against NRAP recognized a 185-kD band on Western blots of skeletal and cardiac muscle proteins.