STUDIES ON DYNAMIC PROPERITIES OF CYTOSKELETAL FILAMENT SYSTEMS

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1) Cytokinesis : It has been shown that both protein phosphorylation and a low molecular weight protein rho are involved in the organization of the contractile ring. 2) In vitro motility : Tropomyosin-troponin enhances efficiency of chemical-mechanical energy transfomation in the actomyosin interaction. Kinesin head domain has been shown to be able to slide microtubules (MTs). 3) Structure-function relationship of actin : Chimera actins have been produced from Tetrahymena and Dictyostelium. A segment spanning from res. 38-83 in the actin sequence has been shown to interact with DNase I.4) Membrance-skeleton interaction : ERM family proteins are involved in constitution of the actin cytoskeleton. These proteins directly interact with the membrane protein CD44.5) Mitotic apparatus : Hexylene glycol, a MT-stabilizer, enlarges metaphase spindle at concentrations less than 3%, and slows chromosome movements. 6) Motility in chromatophores : Ca ion concentration raises prior to aggregation of pigments in melanophores. Pigments moves through interaction between motor proteins and MTs. 7) Brain MTs : An epitope for anti-tubulin antibody E3B8 is present in res. 432-452 which is common in all alpha-tubulins. 8) Dynamic properties of MTs : MTs switch from depolymerization phase to polymerization phase at the site of MAPs binding. The MT-satsbilizing ability of MAPs is abolished by phosphorylation by MPF.22S dynein binds to MTs in an ATP-sensitive manner and thereby stabilizes the MTs. 9) Intermediate filaments : Type 2A phosphatase associates with neurofilaments in the spinal cord and stabilizes the neurofilaments. It ia likely that CaM-kinase II is a intermediate filament-kinase during cell division.