Layout of the Sarcomeric Titin and Nebulin Filament Systems:
Introduction to our product family for sarcomeric epitope mapping:
Myofibrils contain in addition to thick and thin filaments two additional filament systems, formed by the giant polypeptides titin (Mw up to 4.200kDa) and nebulin (Mw 800kDa), respectively.
Top: The titin polypeptide chain locates at its N-terminal and within the Z-disk; its C-terminal end reaches up to the M-line. Below: In electron microscopy, single titin molecules appear as to 2µm long filaments with a beaded substructure. Titin´s modular substructures supports production of antibodies to specific sub-domains .
Bottom: Immuno-electron microscopy studies using 5 distinct domain-specific titin antibodie. Titin epitopes from it’s A-band region are firmly associated with the myosin-based thick filaments (red-white striped). In contrast, titin epitopes within the I-band region correspond to titin´s elastic region. A mix of five titin-epitope specific antibodies was used to identify the region of titin that behaves compliant during myofibrillar stretch (marked in red; see also Trombitas et al., 1998 for more details).
