Gel Filtration Chromatography of Squid Translocator
(A) Microtubule-purified translocator was applied to a Bio-Gel A5m column, and the microtubule-movement-inducing and ATPase activities of the eluant fractions were determined. (B) The polypeptide compositions of fractions 21–45 were analyzed by SDS polyacrylamide gel electrophoresis (60 μl loaded per lane); fraction 30 contains approximately 65 μg/ml of protein. (C) A densitometer scan is shown of a lane from the fraction (30) with the greatest movement-inducing activity from another column. Chromatographic conditions: A 0.75 ml sample of microtubule-purified translocator (which moved microtubules at a 1:20 dilution) was applied to a 1 × 47 cm column equilibrated in 100 mM KCl, 50 mM Tris (pH 7.6), 5 mM MgCI2, 0.5 mM EDTA, and 1 mM ATP. The column was run at 4°C at 5 cm/hr; 0.75 ml fractions were collected. Excluded (Vo) and included (VT) volume fractions are noted at top. Microtubule movement was measured by serial dilution as described in Experimental Procedures. The tubulin doublet at 55 kd that streaks across the gel is not typical, but is an artifact of this particular gel.