EVIDENCE AGAINST STRUCTURAL AND FUNCTIONAL IDENTITY OF MICROTUBULE-ASSOCIATED PROTEIN 1B AND PROTEOGLYCAN CLAUSTRIN

Recently, the concept of microtubule-associated protein 1B as an intra cellular 2460 amino acid protein was challenged by the suggestion that only the N-terminal 1022 codons are utilized and encode the core prot ein of the extracellular proteoglycan claustrin (Burg and Cole (1994) J. Neurobiol. 25, 1-22). We expressed this N-terminal MAP1B fragment i n tissue culture cells and found that it bound to microtubules and was not localized in the extracellular matrix. In addition, epitope mappi ng demonstrated that MAP1B consisted of more than 1022 amino acids and that the reported cDNA of claustrin is incomplete. (C) 1998 Federatio n of European Biochemical Societies.