TY - JOUR
T1 - Participation of guanine nucleotides in nucleation and elongation steps of microtubule assembly.
AU - Karr, T. L.
AU - Podrasky, A. E.
AU - Purich, D. L.
PY - 1979/11
Y1 - 1979/11
N2 - Critical concentrations for formation of microtubules from subunits with GTP and its beta, gamma-imido and beta, gamma-methylene analogs are similar when adequate time is given for equilibration. Dilution of microtubules into GTP and GDP yielded values of 0.1 and 0.19 mg/ml for the critical concentration, results similar to those reported by Carlier and Pantaloni [Carlier, M. & Pantaloni, D. (1978) Biochemistry 17, 1908-1915]. GDP is capable of supporting elongation of preformed microtubules, but it efficiently poisons the nucleation events. Reported experiments also demonstrate that the critical tubulin concentration of the tubulin-GDP complex can be accurately measured in both the assembly and disassembly directions. Evidence is presented that GTP is involved in early nucleation events but that microtubules are stabilized in the presence of either GTP or GDP. These results are discussed in terms of a condensation-equilibrium model in which tubulin subunits equilibrate rapidly with microtubule ends, and their affinity for the ends is governed by the nucleotide ligand at the exchangeable site.
AB - Critical concentrations for formation of microtubules from subunits with GTP and its beta, gamma-imido and beta, gamma-methylene analogs are similar when adequate time is given for equilibration. Dilution of microtubules into GTP and GDP yielded values of 0.1 and 0.19 mg/ml for the critical concentration, results similar to those reported by Carlier and Pantaloni [Carlier, M. & Pantaloni, D. (1978) Biochemistry 17, 1908-1915]. GDP is capable of supporting elongation of preformed microtubules, but it efficiently poisons the nucleation events. Reported experiments also demonstrate that the critical tubulin concentration of the tubulin-GDP complex can be accurately measured in both the assembly and disassembly directions. Evidence is presented that GTP is involved in early nucleation events but that microtubules are stabilized in the presence of either GTP or GDP. These results are discussed in terms of a condensation-equilibrium model in which tubulin subunits equilibrate rapidly with microtubule ends, and their affinity for the ends is governed by the nucleotide ligand at the exchangeable site.
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U2 - 10.1073/pnas.76.11.5475
DO - 10.1073/pnas.76.11.5475
M3 - Article
C2 - 293656
AN - SCOPUS:0018536849
SN - 0027-8424
VL - 76
SP - 5475
EP - 5479
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 11
ER -