Layout of the Sarcomeric Titin and Nebolin 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 4.200.000 kDa) and nebulin (Mw 800 kDa), 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 2 µm 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 withjin 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).
