Re-examination of the Post-translational Arginylated Protein of 125-kD Initially Identified as N-STOP

Author： Decca María Belén Galiano Mauricio R. Barra Héctor S. Hallak Marta E.

ISSN： 0364-3190

Source： Neurochemical Research, Vol.29, Iss.2, 2004-02, pp. : 413-418

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Abstract

Post-translational modification of proteins is a complex mechanism by which cells regulate protein activities. One post-translational modification is the incorporation of arginine into the NH₂-terminus of proteins. It has been hypothesized that in rat brain extracts, one of the proteins modified by this reaction is the microtubule-associated protein Neuronal Stable Tubule Only Polypeptide (N-STOP). This was inferred from its electrophoretic mobility (125 kD) and because it was immunoprecipitated with a monoclonal antibody against the N-STOP. However, this hypothesis is not supported by our recent results. Herein, we found that rat N-STOP interacts with Ca²⁺-calmodulin, whereas the 125-kD [¹⁴C]-arginylated protein does not. The 125-kD [¹⁴C]-arginylated protein from rat brain is separated from the N-STOP by two-dimensional electrophoresis, and it is not recognized by a STOP monoclonal antibody. Mouse brain contains N-STOP, which migrates as a protein of 116 kD and could not be labeled by the post-translational incorporation of [¹⁴C]-arginine. The 125-kD [¹⁴C]-arginylated protein appears in wild-type as well as in STOP knock out mice. Based on these results, we conclude that the 125-kD arginylated protein is different from N-STOP.