Single molecule reconstitution of mRNA transport by a class V myosin

Molecular motors are instrumental in mRNA localization, which provides spatial and temporal control of protein expression and function. To obtain mechanistic insight into how a class V myosin transports mRNA, we performed single-molecule in vitro assays on messenger ribonucleoprotein (mRNP) complexes that were reconstituted from purified proteins and a localizing mRNA found in budding yeast. mRNA is required to obtain a stable processive transport complex on actin, an elegant mechanism to ensure that only cargo-bound motors are motile. Increasing the number of localizing elements (“zipcodes”) on the mRNA, or configuring the track to resemble actin cables, enhanced run length and event frequency. In multi-zipcode mRNPs, motor separation distance varied during a run, showing the dynamic nature of the transport complex. Building the complexity of single-molecule in vitro assays is necessary to understand how these complexes function within cells