Bacterial actin-like proteins: purification and characterization of self-assembly properties.

The sequence, structure, and assembly dynamics of eukaryotic actins are conserved across phyla. In contrast, actin-like proteins (ALPs) from eubacteria share little sequence homology, form polymers with different architectures, and assemble with different kinetics. The structural and functional diversity of the bacterial ALPs appears to arise from their (i) high degree of functional specialization and (ii) small number of regulatory factors. To understand the molecular mechanism by which a given ALP carries out its biological function, we must, therefore, understand its unique architecture and assembly dynamics. In this chapter, we provide a basic toolbox for studying the self-assembly of uncharacterized ALPs, including methods for characterizing the architecture and stability of polymers, specifying the mechanism of their nucleation, and measuring their rate of growth. Determining these basic properties provides a stable base for more complex reconstitutions of biological function.