Tubulin MAP-rich (porcine brain)

Question 1: What is the difference between 70% pure porcine brain tubulin ((Cat. #ML116) and 70% pure bovine brain tubulin (Cat. # ML113)?

Answer 1: The only difference is the source of the tubulin: bovine vs porcine brains. Functionally, there are no significant differences between tubulin isolated from bovine brains vs porcine brains. Stringent quality control and in-house testing has revealed no differences in polymerization, response to drugs (enhancers and inhibitors) or binding to accessory proteins (e.g., motor proteins). (See Comparison of Porcine and Bovine tubulin)

Question 2: Does tubulin polymerization using 70% pure porcine brain tubulin/30% MAPs ((Cat. #ML116) require additional enhancers such as glycerol or taxol?

Answer 2: No additional enhancers are required when using 2 mg/ml of the MAP-enriched 70% pure tubulin. The recommended polymerization reaction using 70% pure tubulin contains 180 &mu, l of 2 mg/ml tubulin in 80 mM PIPES pH 6.9, 0.5 mM EGTA, 2 mM MgCl₂ and 1 mM GTP. Polymerization is started by incubation at 37°C and followed by absorption readings at 340 nm. Under these conditions polymerization reaches a maximal OD340 between 0.3 - 0.4 within 20 minutes. In this experimental set up (180 &mu, l volume in a spectrophotometer with a pathlength of 0.8 cm using Corning Costar&rsquo, s half area well plate Cat. # 3696) an OD340 of 0.16 is approximately equal to 1 mg per ml of tubulin polymer mass. Thus, under the conditions described, approximately 100% of the tubulin is polymerized. If polymerization enhancers such as taxol are to be used or tested, we recommend reducing the tubulin concentration to 1 mg/ml. These conditions will result in a more pronounced nucleation phase and a lower polymerization curve.