Identification of a 34-kD polypeptide as a light chain of microtubule-associated protein-1 (MAP-1) and its association with a MAP-1 peptide that binds to microtubules.
We examined the association of a 34-kD light chain component to the heavy chains of MAP-1 using a monoclonal antibody that specifically binds the 34-kD component and labels neuronal microtubules in a specific and saturable manner. Immunoprecipitation of MAP-1 heavy chains together with the 34-kD component by the antibody indicates that the 34-kD polypeptide forms a complex with MAP-1 heavy chains. Both major isoforms of MAP-1 heavy chains (MAP-1A and MAP-1B) were found in the immunoprecipitate. Digestion of MAP-1 with alpha-chymotrypsin and analysis of the chymotryptic peptides reveals a 120-kD fragment of the MAP-1 heavy chain that binds to microtubules and is precipitable with the 34-kD light chain antibody, suggesting that the 34-kD light chain also binds to this domain of the molecule. Since microtubules that contain the 120-kD fragment lack the long lateral projections characteristic of microtubules with intact MAP-1, the 34-kD light chains may be localized at or near the microtubule surface.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D001923:Brain Chemistry; D002417:Cattle; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D010447:Peptide Hydrolases; D010455:Peptides / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D011485:Protein Binding; D014404:Tubulin / Q000378:metabolism
D000911:Antibodies, Monoclonal; D008869:Microtubule-Associated Proteins; D010455:Peptides; D014404:Tubulin; D010447:Peptide Hydrolases