|Budget Amount *help
¥3,100,000 (Direct Cost : ¥3,100,000)
Fiscal Year 2000 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1999 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1998 : ¥1,300,000 (Direct Cost : ¥1,300,000)
In vertebrate striated muscle, connectin (also called titin ) (MM 3000 kDa) extends from the Z line over the thick filament up to the M line of the sarcomere. One molecule spans a half sarcomere approximately 1.2μm long at rest. On the other hand, in giant sarcomeres of crayfish claw closer muscle the length of which is 8.3μm long at rest, a similar size of an elastic protein functions as connetin. How does the 3000 kDa protein cover such a long distance?
The entire sequence of the 3000 kDa protein was predicted from the cDNA sequences cloned from crayfish claw closer cDNA library. Markedly different sequence from that of vertebrate connectin has been found. First of all, there are novel repeating motifs of 68 and 71 amino acid residues. Second, the number of immunogloblin C2 motif or fibronectin Type III, abundant in vertebrate connectin, is very small. Third, there are two large elastic PEVK domains, as compared to only one domain in vertebrate connectin. Fourth, the myosin light chain kinase domain common to connectin, projectin and twitchin is missing. Immunofluorescence microscopy using antibodies raised to three recombinant peptides demonstrated that the 68 residue repeats and a long spacer between the repeats and immunoglobulin domains were remarkably extensible when the sarcomere was stretched to a sarcomere length of 〜13μm. Furthermore, circular dichroism spectra suggested that a fusion protein of novel 68 repeat consists of 53% β-sheet and 22% β-turn.