Heterologous expression of a cardiomyopathic myosin that is defective in its actin interaction.
A point mutation in the heavy chain of cardiac myosin, resulting in replacement of an arginine (Arg) with glutamine (Gln), has been linked to hypertrophic cardiomyopathy in humans (Geisterfer-Lowrance, A. A. T., Kass, S., Tanigawa, G., Vosberg, H.-P., McKenna, W., Seidman, J. G., and Seidman, C. E. (1990) Cell 62, 999-1006). To determine the functional impact of this mutation, baculovirus-driven coexpression of myosin heavy and light chains has been developed. The Arg-403-->Gln mutation resulted in cardiac myosin with normal ATPase activity in the absence of actin. However, in the presence of actin, ATPase activity was greatly reduced (Vmax decreased > 3.5-fold and K(app) increased > 3-fold). In vitro motility was reduced nearly 5-fold by this single amino acid mutation. Thus, Arg-403 likely contributes to an important interaction at the actin interface of myosin. Replacement of Arg-403 with Gln leads to decreased rate(s) of transition within the actin-myosin crossbridge cycle. In humans, this mutation will result in decreased power output per unit area of cardiac muscle, likely providing a stimulus for hypertrophy.
Sweeney
H L
HL
Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6085.
Straceski
A J
AJ
Leinwand
L A
LA
Tikunov
B A
BA
Faust
L
L
D000199:Actins / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine; D001665:Binding Sites; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics; D027682:Cation Transport Proteins; D002460:Cell Line; D015870:Gene Expression; D005973:Glutamine; D006801:Humans; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding; D051381:Rats; D014162:Transfection
D000199:Actins; D027682:Cation Transport Proteins; D005973:Glutamine; D001120:Arginine; D000251:Adenosine Triphosphatases; C022761:potassium transporting ATPase; D009218:Myosins; D000252:Calcium-Transporting ATPases