Cloning and characterization of a myosin from characean alga, the fastest motor protein in the world

In characean algae, very rapid cytoplasmic streaming is generated by slidin g movement of an unconventional myosin on fixed actin cables. The speed of this sliding movement is the fastest among many molecular motors known so f ar. We have cloned a set of overlapping cDNAs encoding the heavy chain of t his myosin by immunoscreening with antibody raised against characean myosin . The molecular mass of this heavy chain is 248 kDa, and the protein has a conserved motor domain, six IQ motifs, an extensive alpha-helical coiled-co il domain, and a C-terminal globular domain. Phylogenetic analysis suggeste d that this myosin belongs to class XI.