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Invertebrate connectin spans as much as 3.5 μm in the giant sarcomeres of crayfish claw muscle
Author(s) -
Fukuzawa Atsushi,
Shimamura Jinen,
Takemori Shigeru,
Kanzawa Nobuyuki,
Yamaguchi Maki,
Sun Peng,
Maruyama Koscak,
Kimura Sumiko
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.17.4826
Subject(s) - sarcomere , titin , biology , crayfish , anatomy , claw , myosin , microbiology and biotechnology , myocyte , ecology , fishery
In crayfish claw closer muscle, the giant sarcomeres are 8.3 μm long at rest, four times longer than vertebrate striated muscle sarcomeres, and they are extensible up to 13 μm upon stretch. Invertebrate connectin (I‐connectin) is an elastic protein which holds the A band at the center of the sarcomere. The entire sequence of crayfish I‐connectin was predicted from cDNA sequences of 53 424 bp (17 352 residues; 1960 kDa). Crayfish I‐connectin contains two novel 68‐ and 71‐residue repeats, and also two PEVK domains and one kettin region. Kettin is a small isoform of I‐connectin. Immunoblot tests using antibody to the 68‐residue repeats revealed the presence of I‐connectin also in long sarcomeres of insect leg muscle and barnacle ventral muscle. Immunofluorescence microscopy demonstrated that the two repeats, the long spacer and the two PEVK domains contribute to sarcomere extension. These regions rich in charged amino acids, occupying 63% of the crayfish I‐connectin molecule, may allow a span of a 3.5 μm distance as a new class of composite spring.