On the relationship between nucleotide hydrolysis and microtubule assembly: studies with a GTP-regenerating system.
The assembly of pure tubulin dimer has been studied in two buffer systems (containing low and high glycerol/Mg), using a regeneration system protocol to assess the amount of GDP-tubulin in the assembling polymer. For both assembly systems studied, the GDP content is effectively stoichiometric with tubulin throughout assembly. This indicates a high degree of coupling between assembly and GTP-hydrolysis, giving a hydrolysis rate at least 10-fold faster than previously deduced. The steady state GTP hydrolysis rate is quantitatively consistent with this finding. We conclude that the extent of any GTP-tubulin cap is below the detectable limit, both during elongation and at steady state.
D000818:Animals; D002021:Buffers; D002417:Cattle; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D046911:Macromolecular Substances; D008870:Microtubules / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism*
D002021:Buffers; D006150:Guanine Nucleotides; D046911:Macromolecular Substances; D014404:Tubulin; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate