Myomesin 3, a novel structural component of the M-band in striated muscle.
The M-band is the cytoskeletal structure that cross-links the myosin and titin filaments in the middle of the sarcomere. Apart from the myosin tails and the C-termini of titin, only two closely related structural proteins had been detected at the M-band so far, myomesin and M-protein. However, electron microscopy studies revealed structural features that do not correlate with the expression of these two proteins, indicating the presence of unknown constituents in the M-band. Using comparative sequence analysis, we have identified a third member of this gene family, myomesin 3, and characterised its biological properties. Myomesin 3 is predicted to consist of a unique head domain followed by a conserved sequence of either fibronectin- or immunoglobulin-like domains, similarly to myomesin 3 and M-protein. While all three members of the myomesin family are localised to the M-band of the sarcomere, each member shows its specific expression pattern. In contrast to myomesin, which is ubiquitously expressed in all striated muscles, and M-protein, whose expression is restricted to adult heart and fast-twitch skeletal muscle, myomesin 3 can be detected mainly in intermediate speed fibers of skeletal muscle. In analogy to myomesin, myomesin 3 targets to the M-band region of the sarcomere via its N-terminal part and forms homodimers via its C-terminal domain. However, despite the high degree of homology, no heterodimer between distinct members of the myomesin gene family can be detected. We propose that each member of the myomesin family is a component of one of the distinct ultrastructures, the M-lines, which modulate the mechanical properties of the M-bands in different muscle types.
Schoenauer
Roman
R
Institute of Cell Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, CH-8093 Zurich, Switzerland.
Lange
Stephan
S
Hirschy
Alain
A
Ehler
Elisabeth
E
Perriard
Jean-Claude
JC
Agarkova
Irina
I
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001665:Binding Sites; D064211:Connectin; D003599:Cytoskeleton / Q000737:chemistry* / Q000648:ultrastructure; D019281:Dimerization; D004622:Embryo, Mammalian; D000939:Epitopes / Q000737:chemistry; D005091:Exons; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006614:Hindlimb / Q000378:metabolism; D007150:Immunohistochemistry; D007438:Introns; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000378:metabolism / Q000648:ultrastructure; D054792:Muscle, Striated / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D011247:Pregnancy; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D011494:Protein Kinases / Q000737:chemistry* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D012518:Sarcomeres / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D017386:Sequence Homology, Amino Acid; D019170:Somites / Q000378:metabolism
D064211:Connectin; D000939:Epitopes; D009124:Muscle Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C577301:myomesin 3 protein, mouse; D049452:Green Fluorescent Proteins; D005982:Glutathione Transferase; D011494:Protein Kinases