The relationship of bovine intermediate filament proteins. A comparative analysis of glial fibrillary acidic protein, desmin and the neurofilament 70 kDa protein.

Three bovine intermediate filament proteins, glial fibrillary acidic protein, desmin and the 70 kDa component of the neurofilament are compared by cleavage at cysteine and tryptophan. The results of these experiments show that the difference in molecular weight between the glial fibrillary acidic protein and desmin is due to a longer portion of the desmin amino terminal to the tryptophan. On the other hand, the 70 kDa protein contains a carboxy terminal addition. The tryptophan and cysteine contents of these proteins are also determined by amino-acid analysis. Differences in the apparent amount of cysteine determined by these methods in the glial fibrillary acidic protein and 70 kDa proteins are discussed. Interchain disulfide bonds result in the formation of dimers in glial fibrillary acidic protein. The bovine 70 kDa neurofilament protein and desmin also form dimers under nonreducing conditions. This emphasizes the structural similarity of these intermediate filament proteins.