The myofibrillar M‐band in the cryo‐section—analysis of section thickness

Thornell, Lars‐Eric; Sjöstróm, Michael

doi:10.1111/j.1365-2818.1975.tb04024.x

Cited by 19 publications

(3 citation statements)

References 10 publications

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“…In electron micrographs of striated muscle, the M-line appears to be made up of several transverse elements connecting the thick filaments through the bare zone region and gives rise to the typical hexagonal thick filament lattice (Franzini-Armstrong and Porter 1964). Ultrathin frozen sections of muscle show up to nine symmetrically arranged transverse elements (M1-M9 and M1′-M9′) in each half of the M-line structure (Thornell and Sjöström 1975; Sjöström and Squire 1977; Carlsson et al 1990). Immunoelectron microscopic data suggest that MM-CK is part or associated with the prominent M4 and M4′ cross-bridges, also visible by conventional electron microscopy (Wallimann et al 1983a; Wallimann and Eppenberger 1985).…”

Section: Discussionmentioning

confidence: 99%

Isoenzyme-Specific Interaction of Muscle-Type Creatine Kinase with the Sarcomeric M-Line Is Mediated by Nh2-Terminal Lysine Charge-Clamps

Hornemann¹,

Stolz²,

Wallimann³

2000

The Journal of Cell Biology

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Creatine kinase (CK) is located in an isoenzyme-specific manner at subcellular sites of energy production and consumption. In muscle cells, the muscle-type CK isoform (MM-CK) specifically interacts with the sarcomeric M-line, while the highly homologous brain-type CK isoform (BB-CK) does not share this property. Sequence comparison revealed two pairs of lysine residues that are highly conserved in M-CK but are not present in B-CK. The role of these lysines in mediating M-line interaction was tested with a set of M-CK and B-CK point mutants and chimeras. We found that all four lysine residues are involved in the isoenzyme-specific M-line interaction, acting pair-wise as strong (K104/K115) and weak interaction sites (K8/K24). An exchange of these lysines in MM-CK led to a loss of M-line binding, whereas the introduction of the very same lysines into BB-CK led to a gain of function by transforming BB-CK into a fully competent M-line–binding protein. The role of the four lysines in MM-CK is discussed within the context of the recently solved x-ray structures of MM-CK and BB-CK.

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Section: Discussionmentioning

confidence: 99%

Isoenzyme-Specific Interaction of Muscle-Type Creatine Kinase with the Sarcomeric M-Line Is Mediated by Nh2-Terminal Lysine Charge-Clamps

Hornemann¹,

Stolz²,

Wallimann³

2000

The Journal of Cell Biology

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“…). In parallel, it became evident that in negatively stained ultrathin cryosections, the M‐band had distinct lines/striations crosslinking the thick filaments, forming M‐bridges and M‐filaments (Thornell & Sjöström, ). Interestingly, the lines showed a fibre type‐related appearance in human limb skeletal muscle of 3, 3 + 2 or 5 lines (Sjostrom & Squire, ; Fig.…”

Section: Fibre Typing On Basis Of Ultrastructural Variability In M‐bamentioning

confidence: 99%

Fibre typing of intrafusal fibres

et al. 2015

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The first descriptions of muscle spindles with intrafusal fibres containing striated myofibrils and nervous elements were given approximately 150 years ago. It took, however, another 100 years to establish the presence of two types of intrafusal muscle fibres: nuclear bag and nuclear chain fibres. The present paper highlights primarily the contribution of Robert Banks in fibre typing of intrafusal fibres: the confirmation of the principle of two types of nuclear bag fibres in mammalian spindles and the variation in occurrence of a dense M-band along the fibres. Furthermore, this paper summarizes how studies from the Umeå University group (Laboratory of Muscle Biology in the Department of Integrative Medical Biology) on fibre typing and the structure and composition of M-bands have contributed to the current understanding of muscle spindle complexity in adult humans as well as to muscle spindle development and effects of ageing. The variable molecular composition of the intrafusal sarcomeres with respect to myosin heavy chains and M-band proteins gives new perspectives on the role of the intrafusal myofibrils as stretch-activated sensors influencing tension/stiffness and signalling to nuclei.

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“…High resolution electron microscopy using ultrathin cryosections showed that the M-line is actually composed of substriations, with the number of striations varying among different muscle types (32,33). Three structural elements have been identified: primary and secondary (Y-shaped) M-bridges and M-filaments (14,16,20,27,33,39) . Only vague notions exist on the function of this complex structure running across the sarcomere at the height ofthe bare zone of thick myosin filaments (6,10,21).…”

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confidence: 99%

Biochemical and ultrastructural aspects of Mr 165,000 M-protein in cross-striated chicken muscle.

Strehler¹,

Pelloni²,

Heizmann³

et al. 1980

The Journal of Cell Biology

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To better understand the relationship between the Mr 165,000 M-line protein (Mprotein) and H-zone structure in skeletal and in cardiac muscle, as well as the possible interaction of M-protein with another skeletal muscle M-line component, the homodimeric creatine kinase isoenzyme composed of two M subunits (MM-CK), we performed biochemical, immunological, and ultrastructural studies on myofibrils extracted by different procedures .In contrast to MM-CK, M-protein could not be completely removed from myofibrils by low ionic strength extraction . Fab-fragments of antibodies against M-protein could not release Mprotein quantitatively from either breast or heart myofibrils but remained bound to the myofibrillar structure, whereas monovalent antibodies against MM-CK cause the specific release of MM-CK and the concomitant disappearance of the M-line from chicken skeletal muscle myofibrils . When MM-CK was removed from skeletal myofibrils by low ionic strength extraction or, more specifically, by incubation with anti-MM-CK Fab, M-protein was still not released quantitatively upon treatment with anti-M-protein Fab as judged from immunofluorescence data . In the ultrastructural investigation of low ionic strength extracted muscle fibers, M-protein could be localized in two stripes on both sides of the former M-line, suggesting a reduced attachment to the residual H-zone structure, whereas the specific removal of MM-CK resulted in the same dense staining pattern for M-protein within the M-line as observed in untreated fibers . However, the binding of M-protein to the residual M-line structure seemed to be reduced, as a considerable amount of this protein could be identified in the supernate of sequentially incubated myofibrils . The results indicate a strong binding of M-protein within the H-zone structure of skeletal as well as heart myofibrils .

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The myofibrillar M‐band in the cryo‐section—analysis of section thickness

Cited by 19 publications

References 10 publications

Isoenzyme-Specific Interaction of Muscle-Type Creatine Kinase with the Sarcomeric M-Line Is Mediated by Nh2-Terminal Lysine Charge-Clamps

Isoenzyme-Specific Interaction of Muscle-Type Creatine Kinase with the Sarcomeric M-Line Is Mediated by Nh2-Terminal Lysine Charge-Clamps

Fibre typing of intrafusal fibres

Biochemical and ultrastructural aspects of Mr 165,000 M-protein in cross-striated chicken muscle.

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