Fine structure of the A-band in cryo-sections: III. Crossbridge distribution and the axial structure of the human C-zone
JM Squire, JJ Harford, AC Edman… - Journal of Molecular …, 1982 - Elsevier
JM Squire, JJ Harford, AC Edman, M Sjöström
Journal of Molecular Biology, 1982•ElsevierOptical analysis of the C-zones of negatively stained cryo-sectioned A-bands from human m.
tibialis anterior muscle, combined with computer modelling of the C-zone staining pattern,
has led to the following conclusions. 1.(1) At a 99.9% confidence level there are two slightly
different axial repeats in the C-zone. One repeat of 434 (±1.2) Å probably corresponds to the
C-protein repeat, whereas the other of 429 Å (used for calibration) is probably due to myosin
crossbridges. 2.(2) The myosin crossbridge array in (1) does not consist of crossbridge rows …
tibialis anterior muscle, combined with computer modelling of the C-zone staining pattern,
has led to the following conclusions. 1.(1) At a 99.9% confidence level there are two slightly
different axial repeats in the C-zone. One repeat of 434 (±1.2) Å probably corresponds to the
C-protein repeat, whereas the other of 429 Å (used for calibration) is probably due to myosin
crossbridges. 2.(2) The myosin crossbridge array in (1) does not consist of crossbridge rows …
Abstract
Optical analysis of the C-zones of negatively stained cryo-sectioned A-bands from human m. tibialis anterior muscle, combined with computer modelling of the C-zone staining pattern, has led to the following conclusions.
- 1.(1) At a 99.9% confidence level there are two slightly different axial repeats in the C-zone. One repeat of 434 (± 1.2) Å probably corresponds to the C-protein repeat, whereas the other of 429 Å (used for calibration) is probably due to myosin crossbridges.
- 2.(2) The myosin crossbridge array in (1) does not consist of crossbridge rows evenly spaced at 143 Å. The crossbridge positions are periodically shifted from such positions to give a true 429 Å crossbridge repeat.
- 3.(3) The myosin crossbridges are oriented almost perpendicular to the long axis of the muscle; the axial extent of the crossbridge profiles is less than 80 Å.
It is shown that computed model structures which explain satisfactorily the appearances of cryo-sectioned C-zones can also explain several anomalous features of published X-ray diffraction patterns from vertebrate muscle.
Elsevier