Immunoelectron microscopy reveals that a single molecule of nebulin extends along each thin filament with its COOH terminal anchored to the Z-line (plus-end) and the N[H.sub.2] terminal facing the minus-end of the thin filament (Ottenheijm & Granzier).
Consistent with its function, desmin is organized into three domains, a highly conserved [alpha]-helical central region of 308 amino acids and two globular structures, the N[H.sub.2] and COOH terminal regions, known as head and tail domains, respectively (Fig.
Desmin protein is composed by 470 amino acids divided into an [alpha]-helical central zone and two globular structures, the NH2 and COOH terminal regions (known as head and tail domains, respectively).
Titin can act as a "molecular spring" because its NH2 and COOH terminals are strongly anchored to the Z-line and M-line, respectively (Kollar et al.; Tskhovrebova & Trinick, 2010).