Evidence of a new type of protein-protein interaction: desensitized actomyosin blocks Ca(2+)-sensitivity of the natural one. A possible model for an intracellular signalling system related to actin filaments.
Actin filaments are certainly believed to function as an intracellular signalling system; however, this is not confirmed by direct evidence. We used a two-layer actomyosin gel with a concentration gradient of the troponin-tropomyosin complex (TT-complex, Ca(2+)-sensitive system) between the two layers. To prepare one layer of the system, natural actomyosin (nAM) rich in TT-complex was used. To prepare the second layer, we used desensitized actomyosin (dAM) without the complex. All experimental studies were made in medium with a low ionic strength. Two phenomena were observed: (1) dAM blocks Ca(2+)-sensitivity of nAM when the dAM weight portion in the system (as well as in mixed nAM + dAM suspension) reaches 40% and more; further increase of the dAM portion does not affect the Ca(2+)-sensitivity; (2) it was electrophoretically shown that a rapid diffusion of the TT-complex from nAM gel into the dAM gel took place. The apparent diffusion coefficient for the TT-complex in dAM gel is about (1-4).10(-4) cm2/sec, i.e. three orders higher than the same values for protein diffusion in water.
Matveev
V V
VV
Institute of Cytology, Russian Academy of Sciences, St. Petersburg 194064, Russia.
D000199:Actins / Q000502:physiology*; D000205:Actomyosin / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D020013:Calcium Signaling / Q000502:physiology*; D004058:Diffusion; D004591:Electrophoresis, Polyacrylamide Gel; D005782:Gels; D018482:Muscle, Skeletal / Q000737:chemistry; D011489:Protein Denaturation; D011506:Proteins / Q000737:chemistry*; D011817:Rabbits
D000199:Actins; D005782:Gels; D011506:Proteins; D000205:Actomyosin; D002118:Calcium