The entire cDNA sequences of projectin isoforms of crayfish claw closer and flexor muscles and their localization.
Projectin is a giant protein related to twitchin and titin/connectin, that is found in arthropod striated muscle. The complete sequence of a 1 MDa projectin from Drosophila muscle was recently deduced from a thorough analysis of the genomic DNA (Southgate and Ayme-Southgate, 2001). Here we report the complete sequence for projectin from crayfish claw closer muscle (8625 residues; 962,634 Da). The N-terminal sequence contains 12 unique 19-residue repeats rich in glutamic acid (E) and lysine (K). This region, termed the EK region, is clearly distinguishable from the PEVK-like domain of Drosophila projectin. The sequence of crayfish flexor projectin differs from that of closer muscle projectin in that there is a 114-residue deletion and a 35-residue insertion in the N-terminal region. Immunofluorescence microscopy demonstrated that projectin is mainly localized within the sarcomeric A band in both closer and flexor muscles, although the N-terminal region was shown to extrude into the I band region. In the closer muscles, invertebrate connectin (D-titin) connects the Z line to the edge of the A band (Fukuzawa et al., 2001). We have shown that invertebrate connectin is also present in flexor muscle sarcomeres, although in very low abundance.
Oshino
Taichi
T
Department of Biology, Faculty of Science, Chiba University, Chiba 263-8522, Japan.
Shimamura
Jinen
J
Fukuzawa
Atsushi
A
Maruyama
Koscak
K
Kimura
Sumiko
S
D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D003400:Astacoidea / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D018698:Glutamic Acid / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D009132:Muscles / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012518:Sarcomeres / Q000235:genetics / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D002148:Calmodulin-Binding Proteins; D018076:DNA, Complementary; D009124:Muscle Proteins; D020033:Protein Isoforms; C078033:projectin; C489233:unc-22 protein, C elegans; D018698:Glutamic Acid; D008239:Lysine