The regulatory action of alpha-actinin on actin filaments is enhanced by cofilin.

We have used fluorescence recovery after photobleaching to study the effect of muscle alpha-actinin on the structure of actin filaments in dilute solutions. Unexpectedly we found that alpha-actinin partitioned filaments into two types: those with a high mobility and those with low mobility. We have determined that the high mobility (smaller sized) population is too large to be simple monomeric actin:alpha-actinin complexes.

Two proteins from Saccharomyces cerevisiae: Pfy1 and Pkc1, play a dual role in activating actin polymerization and in increasing cell viability in the adaptive response to oxidative stress.

In this work, we show that the proteins Pkc1 and Pfy1 play a role in the repolarization of the actin cytoskeleton and in cell survival in response to oxidative stress. We have also developed an assay to determine the actin polymerization capacity of total protein extracts using fluorescence recovery after photobleaching techniques and actin purified from rabbit muscle. This assay allowed us to demonstrate that Pfy1 promotes actin polymerization under conditions of oxidative stress, while Pkc1 induces actin polymerization and cell survival under all the conditions tested.