Intermediate filament forming ability of desmin derivatives lacking either the amino-terminal 67 or the carboxy-terminal 27 residues.
Amino acid sequence data and results from limited proteolytic digestion have been used to define the three-domain structure of intermediate filament proteins. A centrally located highly alpha-helical domain of about 310 residues well-conserved in sequence principles and length is flanked by the highly variable sequences of the non-alpha-helical headpiece and tailpiece. A direct involvement in filament formation of one or both terminal domains was previously proposed for desmin since chymotryptic removal of head and tailpiece provided a derivative unable to form filaments. In order to evaluate directly the importance of these regions we have prepared desmin derivatives lacking either the amino-terminal 67 (T-desmin) or carboxy-terminal 27 residues (L-desmin). Whereas the latter derivative is fully polymerization-competent the fragment lacking only the basic and arginine-rich headpiece cannot form filaments on its own and remains in a protofilamentous stage. These structures of T-desmin are not incorporated into filaments when mixed with protofilaments of desmin. If, however, the two proteins are mixed in 7 M-urea subsequent dialysis provides morphologically normal filaments containing T-desmin. The results suggest that at least certain hybrid protofilaments containing less than four headpieces are accepted in the filament. The removal of the 27 carboxy-terminal residues in L-desmin, although not interfering with filament formation, leads to a change in surface since filaments show lateral aggregation at 170 mM but not at 50 mM salt. The results are discussed in relation to current models of intermediate filament structure.
D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D003599:Cytoskeleton / Q000648:ultrastructure*; D003893:Desmin; D004591:Electrophoresis, Polyacrylamide Gel; D007382:Intermediate Filaments / Q000648:ultrastructure*; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D010447:Peptide Hydrolases; D011489:Protein Denaturation; D014508:Urea
D003893:Desmin; D046911:Macromolecular Substances; D014508:Urea; D010447:Peptide Hydrolases