Incorporation of radioactive tubulin into microtubules at steady state. Experimental and theoretical analyses of diffusional and directional flux.

摘要: Subunit flux into porcine brain microtubules at steady state has been studied using both radioactive guanine nucleotide and a tubulin dimer, [3H]ethyltubulin, which is obtained by reductive ethylation (Zeeberg, B., Cheek, J., Caplow, M., (1980) Anal. Biochem. 104, 321--327). We have also determined the molecular rate constants for dimer loss from addition to microtubule. This first study where of subunits correlated with measured constants. Also, we derive theoretical analysis observed polymer in pulse chase experiments; this used relate constant model. Analysis our results shows that, state, there only small difference number assembly disassembly events given microtubule end (as compared total ends) unit time; predominant opposite assembly-disassembly (Margolis, R. L., Wilson, L. (1978) Cell 13, 1--8) is, therefore, ruled out. The almost complete absence provides means very efficient regulation network vivo, since modulation relative magnitudes can increase subunit dramatically.