VELOCITY OF TRANSLATION OF SINGLE ACTIN-FILAMENTS (AF) BY MYOSIN HEADS FROM ANTIGEN-SENSITIZED AIRWAY SMOOTH-MUSCLE

We have previously reported increased velocity of shortening (V-0) in the sensitized airway (0.36 1(0)/s, +/- SE) smooth muscle compared to the control (0.26 1(0)/s, +/- 0.017 SE) and subsequent experiments ind icated this was due to increased phosphorylation of the 20 kDa myosin light chain resulting from increased total myosin light chain kinase a ctivity. The motility assay technique described by Kron and Spudich wa s employed to determine whether additionally the molecular motor (acto myosin crossbridge) itself was altered in airway smooth muscle by ragw eed pollen sensitization. The motility assay measures the velocity of actin filament translation by myosin molecules. The negative results o f the motility assay were valuable in determining that the pathogenesi s of allergic bronchospasm is not at contractile protein level but at regulatory enzyme level.