Biopolymers and cell. 1997; 13 (6): 464 - 473

Supramolecular species of smooth muscle tnyosin light chain kinase. 1. Characterization and percent distribution in solution

A. M. Filenko, V. M. Danilova, A. Sobieszek

It is shown by the light scattering methods that inactive (calmodulin-free) myosin light chain kinase (MLCK) exists in solution as a mixture of oligomeric, dimeric and monomeric spicies, which relative concentrations at physiological ionic strength constitute correspondingly 2, 53 and 45 weight percent. After kinase activation by calmodulin (CaM) we could not detect any appreciable changes in the kinase species distribution when either kinase or CaM were present in molar excess. Analysis of the data obtained indicates that the kinase oligomer structure may be interpreted as a kind of flexible spiral in which MLCK molecules associate in head-to-tail fashion with the limiting configurations being a ring, and a long rod. It is important to point out that the spiral-like oligomer fits very well to the helical structure of self-asssembled myosin filaments.