Tang J X, Ito T, Tao T, Traub P, Janmey P A
Division of Experimental Medicine, Brigham and Women's Hospital, Program in Biological and Biomedical Sciences, Harvard Medical School, 221 Longwood Avenue, LMRC 301, Boston, Massachusetts 02115, USA.
Biochemistry. 1997 Oct 14;36(41):12600-7. doi: 10.1021/bi9711386.
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 transition 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.
许多带正电荷的多肽和蛋白质能够使DNA、F-肌动蛋白、微管以及诸如丝状噬菌体fd和烟草花叶病毒（TMV）等病毒聚集，还能使波形蛋白形成的中间丝聚集。这种普遍行为是由这些生物聚合物共有的聚电解质性质决定的，这会导致带有几个净相反电荷的配体发生非特异性结合。一种有吸引力的相互作用导致了随后的横向聚集，这使得这种转变有别于高浓度下丝状颗粒的液晶形成。形态上相似的丝束也可以由惰性溶质如聚乙二醇（PEG）和不与大分子丝结合的蛋白质诱导形成，但这类束转变背后的物理化学性质是不同的。特别是，由静电和空间位阻机制诱导的束转变对溶液离子强度和丝状生物聚合物浓度的依赖性相反。本报告中阐述的不同机制可能各自有助于在生理条件下形成特定的聚合物束。
