Tubulin protein: MAP rich: porcine brain
Product Uses Include
- Studying the effects of MAPs on microtubule dynamics
- Studying the binding sites between MAPs and tubulin.
- Studying the effects of anti-microtubule drugs on microtubule polymerization.
Material
Tubulin and microtubule associated proteins (MAPs) has been purified from porcine brain by an adaptation of the method of Shelanski et al. (1). Tubulin is supplied as a white lyophilized powder. The protein composition is approximately 70% tubulin (55 kDa heterodimer) and 30% MAPs. The MAPs in this product act to stabilize microtubules and to enhance tubulin polymerization. MAP rich tubulin can polymerize efficiently at 1-2 mg/ml.
MAP-rich tubulin is also available from a bovine source (Cat. # ML113).
Purity
Purity is determined by scanning densitometry of proteins on SDS-PAGE gels. Samples are approximately 70% tubulin and 30% MAPs.
Biological Activity
One unit of MAP-rich tubulin is defined as 5.0 mg of protein (as determined by the Precision Red Protein Assay Reagent, Cat. # ADV02). MAP-rich tubulin will polymerize efficiently at protein concentrations above 1mg/ml and temperatures above 24°C.
References
- Shelanski M. L., et al. (1973). Proc. Natl. Acad. Sci. USA. 70, 765-768
For product Datasheets and MSDSs please click on the PDF links below. For additional information, click on the FAQs tab above or contact our Technical Support department at tservice@cytoskeleton.com
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 μl 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 μl volume in a spectrophotometer with a pathlength of 0.8 cm using Corning Costar’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.
If you have any questions concerning this product, please contact our Technical Service department at tservice@cytoskeleton.com
