Actin filament and microtubule, which belong to the cytoskeleton,  are found in all eukaryotic cells, and are essential in many cellular functions, e. g. cell division, intracellular transport, cell morphology, cytoplasmic organization, force generation.   Actin filament and microtubule consist of actin molecule and tubulin molecule, respectively (Fig. 1).   In the cells, several accessory proteins bind to these filament proteins.  Our group is studying about structure and function of these accessory proteins.

(1) Biomolecular motor
 

(2) Actin-regulated protein
     ADF/cofilin family is a low-molecular-mass actin filament-depolymerizing proteins.  In vitro experiments demonstrated that ADF/cofilin binds to filamentous actin in a 1:1 molar ratio of ADF/cofilin to actin monomer, and severs and depolymerizes the filaments.  In eukaryotic cells, the ADF/cofilin family is an essential group of actin regulatory proteins that enhance the turnover of actin by regulating the rate constants of polymerization and depolymerization.

(3) Microtubule-associated protein
     Microtubule-associated proteins (MAPs) copolymerize with microtubules through in vitro cycles of assembly and disassembly, stimulate their polymerization, and stabilize the polymer.  MAPs are believed to regulate the diverse and dynamic functions of microtubules in vivo.  MAPs are classified into two groups: neural MAPs and non-neural MAPs.  Three major neural MAPs (MAP1, MAP2, and tau) and a non-neural MAP (MAP4) have been identified and well characterized at the biochemical level.
 

Techniques