Hierarchical Assembly Pathways of Spermine-Induced Tubulin Conical-Spiral Architectures

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Tubulin, an important cytoskeletal protein, assembles into varied morphologies by interacting with an array of mobile elements. Considered one of these elements is the endogenous polyamine spermine, which can promote and stabilize tubulin assemblies. Nonetheless, the assembled constructions and their formation pathways are poorly recognized. Right here we present that spermine induced the in vitro meeting of tubulin into a number of hierarchical architectures primarily based on a tubulin conical-spiral subunit. Utilizing answer X-ray scattering and cryo-TEM, we discovered that with progressive enhance of spermine focus tubulin dimers assembled into conical-frustum-spirals of accelerating size, containing as much as three helical turns. The subunits with three helical turns had been then assembled into tubules by base-to-top packing and shaped antiparallel bundles of tubulin conical-spiral tubules in a distorted hexagonal symmetry. Additional enhance of the spermine focus led to inverted tubulin tubules assembled in hexagonal bundles. Time-resolved experiments revealed that tubulin assemblies shaped at increased spermine concentrations assembled from intermediates, much like these shaped at low spermine concentrations. These outcomes are distinct from the classical transition between twisted ribbons, helical, and tubular assemblies, and supply perception into the versatile morphologies that tubulin can kind. Moreover, they might contribute to our understanding of the interactions that management the composition and development of protein-based biomaterials.


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