9f3r
13pf E254Q microtubule from recombinant human tubulin decorated with EB3
Structural highlights
FunctionMARE3_HUMAN Binds to the plus end of microtubules and regulates the dynamics of the microtubule cytoskeleton. Promotes microtubule growth. May be involved in spindle function by stabilizing microtubules and anchoring them at centrosomes. May play a role in cell migration (By similarity).[1] Publication Abstract from PubMedA critical feature of microtubules is their GTP cap, a stabilizing GTP-tubulin rich region at growing microtubule ends. Microtubules polymerized in the presence of GTP analogs or from GTP hydrolysis-deficient tubulin mutants have been used as GTP-cap mimics for structural and biochemical studies. However, these analogs and mutants generate microtubules with diverse biochemical properties and lattice structures, leaving it unclear what is the most faithful GTP mimic and hence the structure of the GTP cap. Here, we generate a hydrolysis-deficient human tubulin mutant, alphaE254Q, with the smallest possible modification. We show that alphaE254Q-microtubules are stable, but still exhibit mild mutation-induced growth abnormalities. However, mixing two GTP hydrolysis-deficient tubulin mutants, alphaE254Q and alphaE254N, at an optimized ratio eliminates growth and lattice abnormalities, indicating that these 'mosaic microtubules' are faithful GTP cap mimics. Their cryo-electron microscopy structure reveals that longitudinal lattice expansion, but not protofilament twist, is the primary structural feature distinguishing the GTP-tubulin containing cap from the GDP-tubulin containing microtubule shaft. However, alterations in protofilament twist may be transiently needed to allow lattice compaction and GTP hydrolysis. Together, our results provide insights into the structural origin of GTP cap stability, the pathway of GTP hydrolysis and hence microtubule dynamic instability. Hydrolysis-deficient mosaic microtubules as faithful mimics of the GTP cap.,Estevez-Gallego J, Blum TB, Ruhnow F, Gili M, Speroni S, Garcia-Castellanos R, Steinmetz MO, Surrey T Nat Commun. 2025 Mar 10;16(1):2396. doi: 10.1038/s41467-025-57555-6. PMID:40064882[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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