Identification of new repeating motifs in titin

Repeating motifs of 26-28 amino acids have been identified in the PEVK regi on of the giant elastic protein titin. These motifs, termed PPAK for the fo ur amino acids that often constitute the beginning of the motif, occur 60 t imes in human soleus titin. PPAK motifs occur in groups of 2-12 that are se parated by regions rich in glutamic acid (approximately 45%) and termed pol yE segments. The fluctuation of the net charge between the PPAK and polyE r egions suggests ionic interactions between these segments and their involve ment in the elastic function of titin. (C) 2001 Wiley-Liss, Inc.