Biomolecular motor systems such as actin/myosin and microtubules/kinesin systems are smallest natural machine that convert chemical energy of ATP into mechanical work. They perform various functions in vivo such as cell motility, cytokinesis, cellular transport etc. Although biomolecular motors are able to work alone, their performance is amplified many times when they work together. For example, integrated function of motor proteins is strikingly demonstrated in muscles where biomolecular motors generate power for the contraction of muscles. Sarcomeres, smallest contractile units of muscles, are highly oriented structure primarily composed of actin filaments and myosin filaments (multimeric myosin). Shortening all the sarcomere which is caused by sliding motion between actin filaments and myosin filaments provides rapid contraction of the entire muscle. If we can reproduce such highly organized structure of biomolecular motors in vitro, it will provide muscle like micro soft actuator (artificial muscle).
So far it has reported a successful technique to produce high oriented microtubules with preferential polarity under a temperature gradient (1). They also demonstrated particular unidirectional movement of kinesin on microtubule. However it is still challenging to apply the in vitro biomolecular motor systems for designing artificial muscle.
Microtubules are filamentous and cylindrical biopolymers of the heterodimer of tubulin. They are present in virtually all eukaryotic cells as a major component of an interconnected network of filaments known as the cytoskeleton. They perform various functions not only in cell motility, cell division, organization and orientation but also in transporting organelles as rail for motor proteins.
Kinesin is a motor protein found in eukaryotic cells. It moves along microtubule filaments fueled by the hydrolysis of ATP. It helps transport cellular cargoes and support several cellular functions including mitosis, meiosis and cytokinesis.
Sarcomere is the contractile unit of muscle. It is comprised of actin filaments and bipolar myosin filaments (multimeric myosins) which are organized into high oriented structure. Sliding motion between actin filaments and myosin filaments causes shortening all the sarcomere and subsequently the entire muscle.
In this project we design sarcomere-like structure of muscle using the well-oriented microtubules with preferential polarity under the temperature gradient using photo irradiation. This work will accelerate the development towards the biomolecular motor system based molecular robotics.
(1) Kakugo, A.; Tamura, Y.; Shikinaka, K.; Yoshida, M.; Kawamura, R.; Furukawa, H.; Osada, Y.; Gong, J.P. J. Am. Chem. Soc. 2009, 131, 18089-18095.