Title: Mode of Heavy Meromyosin Adsorption and Motor Function Correlated with Surface Hydrophobicity and Charge
Citation: LANGMUIR vol. 23 no. 22 p. 11147-11156
Publication Year: 2007
JRC N°: JRC41041
ISSN: 0743-7463
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC41041
DOI: 10.1021/la7008682
Type: Articles in periodicals and books
Abstract: The in vitro motility assay is valuable for fundamental studies of actomyosin function and has recently been combined with nanostructuring techniques for the development of nanotechnological applications. However, the limited understanding of the interaction mechanisms between myosin motor fragments (heavy meromyosin, HMM) and artificial surfaces hampers the development as well as the interpretation of fundamental studies. Here we elucidate theHMM-surface interaction mechanisms for a range of negatively charged surfaces (silanized glass and SiO2), which is relevant both to nanotechnology and fundamental studies. The results show that the HMM-propelled actin filament sliding speed (after a single injection of HMM, 120 íg/mL) increased with the contact angle of the surfaces (in the range of 20-80°). However, quartz crystal microbalance (QCM) studies suggested a reduction in the adsorption of HMM (with coupled water) under these conditions. This result and actin filament binding data, together with previous measurements of the HMM density (Sundberg, M.; Balaz, M.; Bunk, R.; Rosengren-Holmberg, J. P.; Montelius, L.; Nicholls, I. A.; Omling, P.; Tågerud, S.; Månsson, A. Langmuir 2006, 22, 7302-7312. Balaz, M.; Sundberg, M.; Persson, M.; Kvassman, J.; Månsson, A. Biochemistry 2007, 46, 7233-7251), are consistent with (1) an HMM monolayer and (2) differentHMMconfigurations at different contact angles of the surface. More specifically, theQCM and in vitro motility assay data are consistent with a model where the molecules are adsorbed either via their flexible C-terminal tail part (HMMC) or via their positively charged N-terminal motor domain (HMMN) without other surface contact points. Measurements of ú potentials suggest that an increased contact angle is correlated with a reduced negative charge of the surfaces. As a consequence, the HMMC configuration would be the dominant configuration at high contact angles but would be supplemented with electrostatically adsorbedHMMmolecules(HMMN configuration) at low contact angles. This would explain the higher initial HMM adsorption (from probability arguments) under the latter conditions. Furthermore, because the HMMN mode would have no actin binding it would also account for the lower sliding velocity at low contact angles. The results are compared to previous studies of the microtubule-kinesin system and are also
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