PEVK segment

Fig. 1. Layout of titin in the sarcomere. Center panel electron micrograph of sarcomere of stretched soleus muscle fiber, labeled with anti-titin antibodies that demarcate the tandem Ig and PEVK spring elements of titin s extensible I-band region. Superimposed are two schematic titin molecules (one for each half sarcomere). Top and bottom panels domain structure of I-band and A-band sequence of titin, respectively (from Labeit and Kolmerer, 1995). Bottom left length of tandem Ig segment (proximal + distal segment) and PEVK segment in human soleus fibers, as function of sarcomere length (based on Trombitas et al., 1998b).

Previous work on N2B titin-expressing myocardium has revealed that the N2B PEVK region and F-actin interact (Kulke et al, 2001 Yamasaki et al, 2001), enhancing passive stiffness. Evidence suggests that this interaction can be inhibited by SI 00, provided that calcium is present (Yamasaki et al., 2002). Whether the PEVK segment of N2BA titin also interacts with actin has not been studied. Considering the different composition of N2B... 

Ma, K., and Wang, K. (2003). Malleable conformation of the elastic PEVK segment of titin Non-cooperative interconversion of polyproline II helix, beta-turn and unordered structures. Biochem.J. 374, 687-695. 

Segment contains tandem Ig repeats and PEVK repeats, both acting as molecular spring elements. This segment is extensively differentially spliced. In the shortest cardiac-specific N2B titin isoform (linked to inclusion of exon 49), exon 50 is spliced direcdy to exon 225. In more compliant cardiac and skeletal titin isoforms, exon 50 is spliced to exon 51 (linked to additional inclusion of exons in the segment 52-224). 

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