CHAPTER FORTY-ONE – Fluorescent Analogues: Optical Biosensors of the Chemical and Molecular Dynamics of Macromolecules in Living Cells

Fluorescent analog cytochemistry has grown to produce important insights in a wide variety of fields. It has been found that a protein labeled with a fluorescent dye could function and be investigated within living cells. Environmentally insensitive fluorescent analogs of many different proteins have been successfully observed in live cells. This chapter discusses subsequent regulatory steps involving the modulation of the calcium signal through calmodulin and myosin light-chain kinase. Calcium binding to calmodulin enables calmodulin to activate myosin light chain kinase, which phosphorylates myosin II regulatory light chains. This phosphorylation activates myosin for contraction. The chapter describes protein-based fluorescent indicators for observation of individual signaling steps in this process and the production and application of fluorescent analogs used as biosensors of calcium–calmodulin binding. It also discusses the progress toward indicators of myosin light chain phosphorylation.