MICROSCOPIC OBSERVATIONS ON INTERACTION OF HEAVY MEROMYOSIN-S-1 AND ACTIN IN MYOFIBRILS

  • 1 January 1975
    • journal article
    • research article
    • Vol. 10  (4) , 267-275
Abstract
The binding of the proteolytic heavy meromyosin fragment, HMM-S-1 [subfragment-1], to the non-overlapping part of actin filaments in intact myofibrils can be demonstrated under the phase contrast microscope as a contrast reversal of striation. The same effect can be seen on ghost myofibrils (after myosin extraction) where the whole length of the I-filaments is bare. HMM-S-1 loaded ghost myofibrils contracted upon addition of ATP in agreement with the recent report of Oplatka et al. but under the same conditions ghost myofibrils not treated with HMM-S-1 also contracted. If the ghosts were prepared under conditions more favorable to myosin extraction, contraction became nil or negligible even when ghosts were loaded with S-1. The effect described by Oplatka''s group is apparently attributed to a small number of residual myosin fliaments in the ghosts.