Novel 130-kDa rat liver myosin-1 will translocate actin filaments.
We have recently purified and characterized from rat liver, polypeptides of 110-kDa and 130-kDa which possess several characteristics of myosin-1 [Coluccio and Conaty: Cell Motil. Cytoskeleton 24:189-199, 1993]. What roles these myosin-1 molecules play in hepatocytes is not yet defined. One hypothesis is that they are involved in either intracellular transport or locomotion. As a first step in establishing their function, we have investigated whether these molecules are capable of supporting motility in vitro. Our results clearly demonstrate that the isolated 130-kDa-calmodulin complex will translocate filaments at a rate of 0.03-0.05 microns/sec; motility is inhibited in free calcium ion concentrations above 0.1 microM. This inhibition is reversed with the addition of exogenous calmodulin. These results provide supporting evidence of a motile role for the 130-kDa-calmodulin complex in vivo. This is the first demonstration that in higher eukaryotes, myosin-1 from a tissue other than intestine will support motility. Partial peptide sequence analysis indicates that the 130-kDa polypeptide resembles the recently described myr 1 [Ruppert et al.: J. Cell Biol. 120:1393-1403, 1993] or MM1 alpha [Sherr et al.: J. Cell Biol. 1405-1416, 1993] gene product.
Williams
R
R
Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322.
Coluccio
L M
LM
D008841:Actin Cytoskeleton / Q000502:physiology*; D000199:Actins / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D002147:Calmodulin / Q000494:pharmacology; D002148:Calmodulin-Binding Proteins / Q000302:isolation & purification* / Q000502:physiology; D008099:Liver / Q000737:chemistry*; D008969:Molecular Sequence Data; D009068:Movement; D024461:Myosin Type I; D009218:Myosins / Q000378:metabolism; D009928:Organ Specificity; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D000199:Actins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; C104297:Myo1b protein, rat; D024461:Myosin Type I; D009218:Myosins