TY - JOUR
T1 - Hierarchical Assembly Pathways of Spermine-Induced Tubulin Conical-Spiral Architectures
AU - Dharan, Raviv
AU - Shemesh, Asaf
AU - Millgram, Abigail
AU - Zalk, Ran
AU - Frank, Gabriel A.
AU - Levi-Kalisman, Yael
AU - Ringel, Israel
AU - Raviv, Uri
N1 - Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/5/25
Y1 - 2021/5/25
N2 - Tubulin, an essential cytoskeletal protein, assembles into various morphologies by interacting with an array of cellular factors. One of these factors is the endogenous polyamine spermine, which may promote and stabilize tubulin assemblies. Nevertheless, the assembled structures and their formation pathways are poorly known. Here we show that spermine induced the in vitro assembly of tubulin into several hierarchical architectures based on a tubulin conical-spiral subunit. Using solution X-ray scattering and cryo-TEM, we found that with progressive increase of spermine concentration tubulin dimers assembled into conical-frustum-spirals of increasing length, containing up to three helical turns. The subunits with three helical turns were then assembled into tubules through base-to-top packing and formed antiparallel bundles of tubulin conical-spiral tubules in a distorted hexagonal symmetry. Further increase of the spermine concentration led to inverted tubulin tubules assembled in hexagonal bundles. Time-resolved experiments revealed that tubulin assemblies formed at higher spermine concentrations assembled from intermediates, similar to those formed at low spermine concentrations. These results are distinct from the classical transition between twisted ribbons, helical, and tubular assemblies, and provide insight into the versatile morphologies that tubulin can form. Furthermore, they may contribute to our understanding of the interactions that control the composition and construction of protein-based biomaterials.
AB - Tubulin, an essential cytoskeletal protein, assembles into various morphologies by interacting with an array of cellular factors. One of these factors is the endogenous polyamine spermine, which may promote and stabilize tubulin assemblies. Nevertheless, the assembled structures and their formation pathways are poorly known. Here we show that spermine induced the in vitro assembly of tubulin into several hierarchical architectures based on a tubulin conical-spiral subunit. Using solution X-ray scattering and cryo-TEM, we found that with progressive increase of spermine concentration tubulin dimers assembled into conical-frustum-spirals of increasing length, containing up to three helical turns. The subunits with three helical turns were then assembled into tubules through base-to-top packing and formed antiparallel bundles of tubulin conical-spiral tubules in a distorted hexagonal symmetry. Further increase of the spermine concentration led to inverted tubulin tubules assembled in hexagonal bundles. Time-resolved experiments revealed that tubulin assemblies formed at higher spermine concentrations assembled from intermediates, similar to those formed at low spermine concentrations. These results are distinct from the classical transition between twisted ribbons, helical, and tubular assemblies, and provide insight into the versatile morphologies that tubulin can form. Furthermore, they may contribute to our understanding of the interactions that control the composition and construction of protein-based biomaterials.
KW - conical-spiral
KW - conical-spiral tubules
KW - inverted tubules
KW - self-assembly
KW - spermine
KW - time-resolved small-angle X-ray scattering
KW - tubulin
UR - http://www.scopus.com/inward/record.url?scp=85106480862&partnerID=8YFLogxK
U2 - 10.1021/acsnano.1c01374
DO - 10.1021/acsnano.1c01374
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C2 - 33900736
AN - SCOPUS:85106480862
SN - 1936-0851
VL - 15
SP - 8836
EP - 8847
JO - ACS Nano
JF - ACS Nano
IS - 5
ER -