Dec 8, 2011
ATP hydrolysis drives microcantilever bending
ATP-hydrolysis induces mechanical motion of a two-dimensional monolayer of gp19 ATPases as measured by coupled movement of an elastic microcantilever plate. Strikingly, the in-plane forces generated by the co-operation of bio-molecular motors produces stepped deflection transitions of the cantilever.
Bio-molecular motors are fascinating nanoscale transducers that turn chemical energy into mechanical work. There is considerable interest in understanding how nature works through these molecular motors and also in designing hybrid synthetic nanomachines of a comparable size and efficiency.
Large irreversible conformational changes
The collaboration between a structural biology group and a biomechanics lab, both based in Madrid, has given rise to a novel measurement of real time conformational changes of viral ATPases. The researchers showed that the nanomechanical response of its device was dependent on the monolayer arrangement of ATPases at the cantilever surface.
The scientists used a surface stress nanomechanical sensor to study the interaction between a monolayer of gp19 ATPases with different nucleotides such as ATP, ADP (the hydrolysis product) and AMP-PNP (a non-hydrolyzable analog). Their results revealed a distinct response of the enzyme to different nucleotides, showing large irreversible conformational changes after the interaction with ATP.
Transforming free energy into motion
As shown in the image, the injection of ATP activates the system in a stepping manner pointing to a coupled release of tensile stress accumulated by the motors during hydrolysis. As a consequence, the team was able to fire and block the activity of the gp19 motors by the consecutive injection of ATP and AMP-PNP (which can also be seen in the image).
These results validate the ability of the researchers' hybrid bionanomechanical system to transform free energy into motion. The sensitivity of this system is up to 1 ng/ml (3 nM), which is an enhancement of two orders of magnitude with respect to conventional methods for the detection of ATPase activity.
The team's understanding and control of the force generation has implications not only in assessing the ATP-driven motors motility potential, but also in the development of active nanodevices and sensors. Although this study is in its preliminary phases, the work reveals exciting opportunities to adsorb chemical species for the study of enzymatic functions.
Additional information can be found in the journal Nanotechnology.
About the author
Johann Mertens is a Ramon y Cajal research fellow at the Bionanomechanics lab of the Madrid Microelectronics Institute. His research interests include nanomechanical biosensors, surface chemistry and NEMS. María I Daudén is a PhD student of Prof. Jose L Carrascosa and she performed the purification and sample preparation of the gp19 ATPase. Prof. Jose L Carrascosa is head of the Department of Structure of Macromolecules at the National Biotechnology Center (CNB) in Madrid. He is a specialist on viral assembly and the structural characterization of the macromolecular complexes involved. Javier Tamayo is group leader of the Bionanomechanics Lab at the Madrid Microelectronics institute. His research has focused on the characterization and study of micro- and nanomechanical structures to develop new paradigms for ultrasensitive biological sensing.