Then they compared the sequences of the fifteen known myosins to look for significant differences in the region corresponding to the molecule's lever arm. Myosin VI promptly emerged as a candidate for consideration because of a 53-amino-acid insertion in the relevant part of the molecule.
Graduate student Amber L. Wells, BS, lead author on the study, devised a motility assay that differentially labeled the plus and minus ends of actin filaments with a fluorescent dye, allowing the researchers to use a fluorescence microscope to see which direction the myosin molecules moved on the filaments when exposed to an energy source, ATP.
"When we looked, we saw that all the other myosin molecules moved in the direction scientists had thought all myosins must move in," Sweeney says. "Myosin VI, however, moved in the opposite direction." Class VI myosins were first discovered in 1992 in fruit flies. Since then, they have been found in life forms ranging from worms to humans on the scale of organizational complexity.
In addition to Sweeney and Wells, the other Penn-based authors on the
study are Li-Qiong Chen, MD, and Daniel Safer, PhD. The other coauthors are Abel
W. Lin, BS, Shane M. Cain, BS, and Ronald A. Milligan, PhD, at The Scripps
Research Institute, Tama Hasson, PhD, at the University of California, San
Diego, and Bridget O. Carragher, PhD, at the University of Illinois at
Urbana-Champaign. Funding for the work was
'"/>
Contact: Franklin Hoke
hokef@mail.med.upenn.edu
215-349-5659
University of Pennsylvania School of Medicine
30-Sep-1999