Investigating Myosin Light Chain Kinase Binding with Actin in Human Airway Smooth Muscle Cells

Abstract

Myosin light chain kinase plays an integral role in initiating and regulating smooth muscle contraction. These experiments were conducted to help illuminate and better understand the process by which myosin light chain kinase interacts with actin and myosin in the ventral stress fibers of permeabilized human airway smooth muscle cells. The first 75 residues of the N-terminal end of MLCK (GST tagged N75) contain the three DFRXXL motifs, which are sufficient for actin binding [1-4]. N75 binding to actin was imaged using fluorescence microscopy and total internal reflection microscopy under varying conditions. N75 binding was inhibited when cells were pre-treated with the S1 fragment of myosin heads. This suggests that the DFRXXL motifs of MLCK are competing with S1 for actin binding sites. These experiments help better the understanding of the role myosin light chain kinase plays in the regulation and contraction of smooth muscle contraction.