Opposite Effects of Electrostatics and Steric Exclusion on Bundle Formation by F-Actin and Other Filamentous Polyelectrolytes†

Jay X. Tang, Tadanao Ito, Terence Tao, Peter Traub, Paul A. Janmey
1997 Biochemistry  
A number of positively charged polypeptides and proteins bundle DNA, F-actin, microtubules, and viruses such as filamentous phage fd and tobacco mosaic virus (TMV), as well as intermediate filaments formed by vimentin. The general behavior is dictated by the common polyelectrolyte nature of these biopolymers, which gives rise to nonspecific binding by ligands carrying several net opposite charges. An attractive interaction accounts for the subsequent lateral aggregation, distinguishing this
more » ... sition from the liquid crystalline formation of filamentous particles at high concentrations. Morphologically similar filament bundles can also be induced by inert solutes such as polyethylene glycol (PEG) and proteins that do not bind the macromolecular filaments, but the physicochemistry underlying this class of bundle transitions is distinct. In particular, bundling transitions induced by electrostatic and steric mechanisms have an opposite dependence on the solution ionic strength and the concentration of the filamentous biopolymers. The distinct mechanisms illustrated in this report may each contribute to the formation of specific polymer bundles under physiological conditions.
doi:10.1021/bi9711386 pmid:9376366 fatcat:2iuu3egao5bnrosdgtbsksrbg4