Connectin, an Elastic Protein from Myofibrils1

Abstract

The elastic protein isolated from myofibrils of chicken skeletal muscle was compared with extracellular non-collagenous reticulin prepared from chicken liver and skeletal muscle. The amino acid compositions of these proteins were similar except that their contents of Phe, Leu, Cys/2, and Hyp were different. The impregnations of the elastic protein and reticulin with silver were also different. The reticulin was not at all elastic. It also differed from reticulin in solubility and antigenicity. It is proposed to call the intracellular elastic protein connectin.

Nuances of electrophoresis study of titin/connectin

“…Independent of Kuan Wang and his coworkers, another group of investigators headed by Koscak Maruyama discovered a protein which they named connectin (Maruyama 1976;Maruyama et al 1976). The properties of connectin as a protein candidate for the elastic filaments in sarcomeres of striated muscles of vertebrate animals were intensively explored by this group of authors in the late 1970s to early 1980s (Maruyama et al 1977a, b, c;Matsubara and Maruyama 1977;Toyoda and Maruyama 1978).…”

Mutation that dramatically alters rat titin isoform expression and cardiomyocyte passive tension

“…Titin [1], also known as connectin [2], is an extremely large protein (subunit weight exceeding 3 MDa) found primarily in cardiac and skeletal muscles. The protein has been implicated in a number of functions, including protection of the sarcomere against overstretch, centering the A band between the Z lines in the sarcomere, sarcomere assembly, serving as a template for length determination of the thick filaments, the source of passive tension, lengthening force from very short sarcomere lengths, phosphorylation of telethonin, control of protein turnover, binding more than 20 other proteins, and participation in signaling pathways in response to muscle stretch (see [3][4][5][6][7] for reviews).…”

Distinct roles for telethonin N‐versus C‐terminus in sarcomere assembly and maintenance

“…In mature striated muscle, it provides passive muscle elasticity (Maruyama, 1976;Maruyama et al, 1977;Mitsui et al, 1987), and has been proposed to act as a stretch sensor (Knöll et al, 2002;Miller et al, 2004;Linke, 2008). During sarcomere assembly, titin is hypothesized to act as a molecular ruler and organizational scaffold (Fü rst et al, 1988;Maruyama, 1976;Maruyama et al, 1985, Trinick, 1994.…”

“…In mature striated muscle, it provides passive muscle elasticity (Maruyama, 1976;Maruyama et al, 1977;Mitsui et al, 1987), and has been proposed to act as a stretch sensor (Knöll et al, 2002;Miller et al, 2004;Linke, 2008). During sarcomere assembly, titin is hypothesized to act as a molecular ruler and organizational scaffold (Fü rst et al, 1988;Maruyama, 1976;Maruyama et al, 1985, Trinick, 1994. Therefore, titin must be rigidly and precisely anchored within the sarcomere, and this is accomplished in part by a small 19-kDa Z-disc protein called telethonin, also known as T-cap (Valle et al, 1997;Gregorio et al, 1998;Zou et al, 2003Zou et al, , 2006Pinotsis et al, 2006).…”