Final Report: Measurement of Velocity Fluctuations to Infer Attachment Geometry and Interactions of Mechanically Coupled Molecular Motors in One-Dimensional Arrays
Abstract
Motor proteins such as myosin or kinesin play a major role in cellular cargo transport, muscle contraction, cell division, and also in engineered nano devices. Quantifying the collective behavior of coupled motors is critical for our understanding of these systems. An excellent model system is the gliding motility assay, where hundreds of surface-adhered motors propel one cytoskeletal filament such as anactin filament or a microtubule. The filament motion can be observed using fluorescence microscopy, revealing fluctuations in gliding velocity. These velocity fluctuations have been previously quantified by a motional diffusion coefficient, which Sekimoto and Tawada explained as arising from the addition and removal of motors from the linear array of motors propelling the filament as it advances assuming that different motors are not equally efficient in their force generation. A computational model of kinesin head diffusion and binding to the microtubule allowed us to quantify the heterogeneity of motor efficiency arising from the combination of an harmonic tail stiffness and varying attachment geometries assuming random motor locations on the surface and an absence of coordination between motors. Knowledge of the heterogeneity allows the calculation of the proportionality constant between the motional diffusion coefficient and the motor density. The calculated value (0.3) is within a standard error of our measurements of the motional diffusion coefficient on surfaces with varying motor densities calibrated by landing rate experiments. This allowed us to quantify the loss in efficiency of coupled molecular motors arising from heterogeneity in the attachment geometry.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 27, 2016
- Accession Number
- AD1063080
Entities
People
- Henry Hess
Organizations
- Columbia University