title: Assembly of unfertilized sea urchin egg tubulin at physiological temperatures.
abstract: Tubulin was purified from unfertilized eggs of the sea urchin Strongylocentrotus purpuratus by DEAE-column chromatography and cycles of temperature-dependent assembly and disassembly. Tubulin-containing column fractions self-assemble into intact microtubules in the absence of high molecular weight microtubule-associated proteins. Egg microtubules assembled during the third cycle of assembly following DEAE-chromatography are composed of 2 or 3 alpha tubulins and 2 beta tubulins as assayed by isoelectric focusing and two-dimensional electrophoresis. The critical protein concentrations necessary for assembly of egg tubulin at 37 and 25 degrees C are 0.15-0.24 and 0.24-0.28 mg/ml, respectively. At physiological temperatures, the critical protein concentrations are 0.81 mg/ml at 15 degrees C and 0.70-0.79 mg/ml at 18 degrees C. At 18 degrees C, bovine brain microtubule-associated proteins stoichiometrically stimulate the initial rate and final extent of egg tubulin assembly. These hybrid microtubules assemble at 18 degrees C at a critical protein concentration of 4-20 micrograms/ml.
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000502:physiology; D005260:Female; D005306:Fertilization; D007700:Kinetics; D046911:Macromolecular Substances; D008297:Male; D008854:Microscopy, Electron; D008870:Microtubules / Q000648:ultrastructure; D008970:Molecular Weight; D010063:Ovum / Q000502:physiology*; D012617:Sea Urchins; D014404:Tubulin / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; D014404:Tubulin