Group:MUZIC: Difference between revisions

==Introduction==

Although all types of muscle cells use actin and myosin for contraction, only in skeletal and cardiac muscle these proteins are organized into sarcomeric units. They are generally composed of ordered thick (myosin) and thin (actin, tropomyosin, troponin) filaments that slide past each other during contraction. The precise ultra-structural order of these filaments is of utmost importance for converting the molecular interactions produced by actin and myosin in each sarcomere into efficient contraction at the macroscopic level (Figure 1). In addition to those components responsible for active muscle operation, many other filamentous proteins, such as titin and nebulin, have important roles in myofibril structure formation and regulation. Titin, the largest known vertebrate gene product, connects the Z-discs to the central M-band [reviewed in <ref>PMID:16337382</ref>] and nebulin, which spans the length of the actin filaments [reviewed in <ref name="r1">PMID:12142273</ref><ref>PMID:22375125</ref><ref>PMID:16230109</ref>].  

One of the functionally most complex sub-compartments of the sarcomere is the Z-disc that forms the lateral boundaries between adjacent sarcomeres. This region plays a central role as the site organizing thick filaments and titin into the molecular machinery that is required for muscle contraction and comprises the actin, titin, and nebulin filaments.