Caldesmon tethers myosin V to actin and facilitates in vitro motility.
The current study examines the hypothesis that caldesmon can facilitate the interaction of myosin V with actin filaments by tethering myosin V to actin. Myosin V, purified from bovine brain stem, translocated actin filaments in an in vitro motility assay at a velocity of 0.30+/-0.05 microm/s in the absence of caldesmon at a myosin concentration of 50 microg/ml (ionic strength=110 mM). Filament binding and motility was absent when the myosin concentration applied to the coverslip was reduced to 5 microg/ml, however, the addition of 0.4 microM caldesmon restored binding and motility (0.28+/-0.06 microm/s). This restoration of motility in the presence of caldesmon was blocked by an N-terminal fragment of caldesmon that competitively inhibits the binding of intact caldesmon to myosin. Similar to previous findings with both smooth muscle myosin and platelets (Haeberle et al., 1992; Hemric et al., 1994), these results demonstrate that caldesmon can form a mobile tether that maintains the proximity of myosin V with actin filaments without restricting filament sliding.
Nibbelink
Brian
B
Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.
Hemric
Mark E
ME
Haeberle
Joe R
JR
D000199:Actins / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000276:immunology; D001667:Binding, Competitive; D002148:Calmodulin-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D002417:Cattle; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D007700:Kinetics; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000378:metabolism*; D024701:Myosin Type V / Q000032:analysis / Q000378:metabolism*; D016501:Neurites / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry; D011485:Protein Binding; D051381:Rats; D017783:Superior Cervical Ganglion / Q000737:chemistry
D000199:Actins; D000906:Antibodies; D002148:Calmodulin-Binding Proteins; D020409:Molecular Motor Proteins; D010446:Peptide Fragments; D024701:Myosin Type V