Actin tube formation: effects of variations in commonly used solvent conditions.

Crystalline tubular aggregates of actin spontaneously assemble in the presence of certain of the lanthanide ions. These tubes are now known to contain a high degree of structural order and it has been suggested that they may be sensitive to small changes in the primary sequence. However, there have been no detailed studies of the effects of solution conditions associated with their formation. In this report we systematically examine the effects of lanthanide ion concentration, ionic radius, adenosine nucleotide concentration, divalent cation concentration, pH, KCl concentration and incubation time. The stringent control of these parameters leads to a high degree of predictability of the structural parameters of the tubes and will thus be of use in identifying actin isozymes.