Transformation of taxol-stabilized microtubules into inverted tubulin tubules triggered by a tubulin conformation switch.
Bundles of taxol-stabilized microtubules (MTs)--hollow tubules comprised of assembled αβ-tubulin heterodimers--spontaneously assemble above a critical concentration of tetravalent spermine and are stable over long times at room temperature. Here we report that at concentrations of spermine several-fold higher the MT bundles (B(MT)) quickly become unstable and undergo a shape transformation to bundles of inverted tubulin tubules (B(ITT)), the outside surface of which corresponds to the inner surface of the B(MT) tubules. Using transmission electron microscopy and synchrotron small-angle X-ray scattering, we quantitatively determined both the nature of the B(MT)-to-B(ITT) transformation pathway, which results from a spermine-triggered conformation switch from straight to curved in the constituent taxol-stabilized tubulin oligomers, and the structure of the B(ITT) phase, which is formed of tubules of helical tubulin oligomers. Inverted tubulin tubules provide a platform for studies requiring exposure and availability of the inside, luminal surface of MTs to MT-targeted drugs and MT-associated proteins.
Materials Department, Physics Department, Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, CA 93106, USA.
Miguel A
MA
Ojeda-Lopez
Materials Department, Physics Department, Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, CA 93106, USA.
Daniel J
DJ
Needleman
Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea.
Chaeyeon
C
Song
Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel.
Avi
A
Ginsburg
Materials Research Laboratory, University of California, Santa Barbara, CA 93106, USA.
Phillip A
PA
Kohl
Materials Research Laboratory, University of California, Santa Barbara, CA 93106, USA.
Youli
Y
Li
Molecular, Cellular, & Developmental Biology Department & Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, USA.
Herbert P
HP
Miller
Molecular, Cellular, & Developmental Biology Department & Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, USA.
Leslie
L
Wilson
Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel.
Uri
U
Raviv
Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea.
Myung Chul
MC
Choi
Materials Department, Physics Department, Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, CA 93106, USA.
Cyrus R
CR
Safinya
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D008870:Microtubules / Q000737:chemistry* / Q000648:ultrastructure*; D017239:Paclitaxel / Q000737:chemistry*; D011485:Protein Binding; D014404:Tubulin / Q000737:chemistry* / Q000648:ultrastructure*
D014404:Tubulin; D017239:Paclitaxel