Limited chymotryptic digestion of bovine adrenal 190,000-Mr microtubule-associated protein and preparation of a 27,000-Mr fragment which stimulates microtubule assembly.
A heat stable microtubule-associated protein of Mr 190,000 (190-kDa MAP) has been purified from bovine adrenal cortex (Murofushi, H., Kotani, S., Aizawa, H., Hisanaga, S., Hirokawa, N., and Sakai, H. (1986) J. Cell Biol. 103, 1911-1919). Limited chymotryptic digestion of 190-kDa MAP produced a fragment of Mr 27,000 (27-kDa fragment), which bound to microtubules reconstituted in the presence of taxol. This fragment was purified with the aid of cosedimentation with microtubules. The purified 27-kDa fragment showed an ability to stimulate tubulin polymerization in the absence of taxol. Electron microscopic observation of microtubules reconstituted from purified 27-kDa fragment and tubulin revealed that the microtubules were in the form of thick bundles and that lateral projections which can be seen in microtubules reconstituted from intact 190-kDa MAP and tubulin were not observed. These results indicate that 27-kDa fragment includes or is a part of microtubule-binding domain of 190-kDa MAP and that this fragment is active in stimulating microtubule assembly. Amino acid analysis revealed that the 27-kDa fragment was rich in lysine, proline, and alanine, the sum of these three being about 45% of the total amino acids and that the contents of methionine, tyrosine, phenylalanine, and histidine were very low. These data suggest that the microtubule binding domain of the 190-kDa MAP comprises an unique structure.
D000302:Adrenal Cortex / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000378:metabolism*; D005613:Freeze Etching; D007700:Kinetics; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification
D008869:Microtubule-Associated Proteins; D010446:Peptide Fragments; D002918:Chymotrypsin