HOTANI Molecular Dynamic Assembly


Research Director: Dr. Hirokazu Hotani
(Professor, Faculty of Science and Technology, Teikyo University)
Research Term: 1986-1991


A search was made for ways to utilize the characteristics of supramolecules for engineering "intelligent" molecular biosensor and biochip systems capable of sensing, processing and judging external information. Specifically, by utilizing methods of embedding proteins in membranes and of artificially modifying proteins, attempts were made to endow single supramolecules with multiple functions.

Research Results

Orientation of flagellar filaments: For x-ray diffraction analyses, a method was developed using superconductive magnets to achieve a sufficient orientation of flagellar filaments in high density.

Supramolecular structure of flagellar filaments: The flageller shape and its 3-dimensional structure have been determined by an x-ray fiber diffraction method.

Molecular dynamic recognition of flagellin: X-ray diffraction and other physico-chemical techniques have revealed that flagellin, the basic building block of flagella, is a multi-domained protein. Various techniques have been used to show that the binding domain of a monomer flagellin is flexible, instead of having a solid 3-dimensional structure.

Formation of flagellar system: It has been found that in the binding between the spiral-shaped screw part and the hook part of a flagellum, two kinds of binding proteins are involved and that each has different properties.

Microtuble assembly within liposomes: The microtuble assembly within liposomes has been developed. It has also been shown that the polymerization of microtubule causes morphological changes of liposomes, producing a good model for cellular morphogenesis.

Control of microtuble formation: Microtubles function freely in the formation and dissemble of cellular organelless, sometimes even serving as rails for carrying small membrane vesicles. For switching over among the various roles, control of the formation and assembly is indispensable.

Direct observation of the rotation speed of a flagellar motor: Recent improvements in the optical microscope and the utilization of laser technology have permitted direct measurements of the rotation of the flagella motor.

Analysis of the molecular assembly of the flagellar motor: The flagellar motor comprises ten kinds of proteins. Efforts were made to elucidate the functions of each protein. These included both disassembling the motor and genetic engineering to over-produce the proteins and to assemble each part.


Structure of bacterial flagellar filament as revealed by X-ray fiber diffraction


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