R. Williams et Lm. Coluccio, NOVEL 130-KDA RAT-LIVER MYOSIN-1 WILL TRANSLOCATE ACTIN-FILAMENTS, Cell motility and the cytoskeleton, 27(1), 1994, pp. 41-48
We have recently purified and characterized from rat liver, polypeptid
es of 110-kDa and 130-kDa which possess several characteristics of myo
sin-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 chat they are involved in either intracellu
lar transport or locomotion. As a first step in establishing their fun
ction, we have investigated whether these molecules are capable of sup
porting motility in vitro. Our results clearly demonstrate that the is
olated 130-kDa-calmodulin complex will translocate filaments at a rate
of 0.03-0.05 mu m/sec; motility is inhibited in free calcium ion conc
entrations above 0.1 mu M. This inhibition is reversed with the additi
on of exogenous calmodulin. These results provide supporting evidence
of a motile role for the 130-kDa-calmodulin complex in vivo. This is t
he first demonstration that in higher eukaryotes, myosin-1 from a tiss
ue other than intestine will support motility. Partial peptide sequenc
e analysis indicates that the 130-kDa polypeptide resembles the recent
ly 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 produ
ct. (C) 1994 Wiley-Liss, Inc.