| The Living State - Albert
Szent-Györgyi
Symposium Pécs University, Sümeg, May 21-24, 2002, Hungary |
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Evidence
of a New Type of Protein-Protein Interaction
Demonstrated by Actomyosin V.
V. Matveev Abstract: Actin filaments are certainly believed to function as an intracellular signalling system; however, this is not confirmed by direct evidence. New properties of actomyosin were found, which might help solving this problem. We used a two-layer actomyosin gel with a concen-tration gradient of the troponin-tropomyosin complex (TT-complex, Ca2+-sensitive system) between the two layers. To prepare one layer of the system, natural actomyosin (nلي) rich in TT-complex was used. To prepare the second layer, we used desensitized actomyosin (dAM) without the complex. All experiments were performed in the medium with a low ionic strength. Three phenomena were observed: (1) dAM blocks Ca2+-sensitivity of nAM when the dAM weight portion in the system (as well as in the mixed nAM+dAM suspension) reaches 40% and more; further increase of the dAM portion does not affect the Ca2+-sensitivity; (2) This interaction begins at a definite nAM/dAM threshold (critical) ratio; (3) it was electrophoretically shown that a rapid diffusion of the TT-complex from the nAM gel into the dAM gel took place. The apparent diffusion coefficient for the TT-complex in the dAM gel is about (1-4)10-4 cm2/sec, i.e. three orders higher than the same values for protein diffusion in water. Additions to a two-component suspension of ethanol or n-propanol restore the Ca2+-sensitivity of nAM blocked by 40% dAM. CONCLUSIONS: (i) the studied protein complexes interact in the gel state; (ii) the interaction begins at a surface of interacting gel particles and extends over the entire gel volume; (iii) the interaction of actomyosin gels reversibly disturbs normal operation of the Ca2+-sensitivity system and can change the TT-complex distribution in the whole gel volume.
Full text of Matveev's report |