TY - JOUR
T1 - Ultrastructural localization of M-band proteins in chicken breast muscle as revealed by combined immunocytochemistry and ultramicrotomy
AU - Strehler, Emanuel E.
AU - Carlsson, Eva
AU - Eppenberger, Hans M.
AU - Thornell, Lars Eric
N1 - Funding Information:
The authors are indebted to Mrs B. Holmbom for expert technical assistance and to Dr T. Wallimann for many helpful discussions. This work was supported by the Swiss National Science Foundation (grant no. 3.187-0.77), the Swedish Medical Research Council (12X-3934) and by a grant from the Muscular Dystrophy Association of America to H.M.E. One of the authors (E.E.S.) acknowledges support from the European Molecular Biology Organization during the tenure of a short term fellowship.
PY - 1983/5/15
Y1 - 1983/5/15
N2 - Cryo-ultramicrotomy and "conventional" plastic sectioning have been used in combination with extraction and immunolabeling techniques to determine the location of the two M-band proteins characterized to date, MM-creatine kinase (MM-CK: Mr, 80,000) and M-protein "myomesin" (Mr, 165,000) within the M-region of chicken pectoralis muscle. The following main results were obtained.o(1)The M-band in chicken pectoralis muscle contains five major striations (M1, M4 and M4′, M6 and M6′ in the terminology of Sjöström & Squire, 1977a).(2)Extraction of the bulk of the electron-dense M-band with low ionic strength removes the M-striations M1, M4 and M4′ while M6 and M6′ are retained. Cross-sections through the M-region of such muscles lack primary M-bridges connecting the thick myosin filaments.(3)Labeling with antibodies against MM-CK enhances the M-striations M4 and M4′; sometimes the whole region beteen M4 and M4′ is labeled.(4)Incubation with antibodies against myomesin results in the labeling of the whole M-band from M6 to M6′; no label is found in the rest of the bare zone outside M6 and M6′.(5)Incubation of low ionic strength extracted muscle fibers with antibodies against myomesin leads to an "incomplete" labeling of the M-band between M6 and M6′; lines M6 and M6′ are sometimes seen to be enhanced presumably due to antibody labeling. From these results it is concluded that MM-CK is the major protein of the M4 and M4′ (and possibly also of the M1) M-bridges. Myomesin is bound within the M-band along the thick filaments from M6 to M6′. Two hypothetical models for the possible location of myomesin are discussed. According to these models myomesin would either make up the M-filaments or be directly attached to and along the central bare zone of thick myosin filaments.
AB - Cryo-ultramicrotomy and "conventional" plastic sectioning have been used in combination with extraction and immunolabeling techniques to determine the location of the two M-band proteins characterized to date, MM-creatine kinase (MM-CK: Mr, 80,000) and M-protein "myomesin" (Mr, 165,000) within the M-region of chicken pectoralis muscle. The following main results were obtained.o(1)The M-band in chicken pectoralis muscle contains five major striations (M1, M4 and M4′, M6 and M6′ in the terminology of Sjöström & Squire, 1977a).(2)Extraction of the bulk of the electron-dense M-band with low ionic strength removes the M-striations M1, M4 and M4′ while M6 and M6′ are retained. Cross-sections through the M-region of such muscles lack primary M-bridges connecting the thick myosin filaments.(3)Labeling with antibodies against MM-CK enhances the M-striations M4 and M4′; sometimes the whole region beteen M4 and M4′ is labeled.(4)Incubation with antibodies against myomesin results in the labeling of the whole M-band from M6 to M6′; no label is found in the rest of the bare zone outside M6 and M6′.(5)Incubation of low ionic strength extracted muscle fibers with antibodies against myomesin leads to an "incomplete" labeling of the M-band between M6 and M6′; lines M6 and M6′ are sometimes seen to be enhanced presumably due to antibody labeling. From these results it is concluded that MM-CK is the major protein of the M4 and M4′ (and possibly also of the M1) M-bridges. Myomesin is bound within the M-band along the thick filaments from M6 to M6′. Two hypothetical models for the possible location of myomesin are discussed. According to these models myomesin would either make up the M-filaments or be directly attached to and along the central bare zone of thick myosin filaments.
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U2 - 10.1016/S0022-2836(83)80003-5
DO - 10.1016/S0022-2836(83)80003-5
M3 - Article
C2 - 6854641
AN - SCOPUS:0021104079
SN - 0022-2836
VL - 166
SP - 141
EP - 158
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 2
ER -