Incorporation of tyrosine analogues into the c-terminus of a-tubulin

ZAMPAR, G.G., BISIG, C.G., PURRO, S.A. AND ARCE, C.A

Pinamar, Argentina

Congreso; Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular (SAIB).; 2005

a-tubuline is biosynthesized with a tyrosine at its C-terminus which can be removed by tyrosine carboxipeptidase and re-incorporated by tubulin tyrosine ligase. We study the capability of the ligase to ioncorporate tyrosine analogues into tubulin. Azatirosine induces the reversion of cancerous phenotype and can be incorporated into the tubulin's C-terminus as well as into proteins via de novo synthesis. Which of these two mechanism is responsible of this effect remains unclear. The introduction of a nitro group into the positron 3 of the phenolic ring of tyrosine avoids its incorporation into proteins via de novo synthesis, but not into tubulin?s C-terminus. Therefore, 3-Nitroazatirosine was synthesized, purified by TLC and characterized by UV-Visible, IR mass and RNM-1H spectroscopy. It was found that 3-nitroazatyrosine couldn?t be
 incorporated into proteins via de novo synthesis nor into tubulin's C-terminus. No effect was found in cellular proliferation. We also studied if the Iigase was able to incorporate other tyrosine analogues. Melphalan could not be incorporated, Thienylalanine and p-aminophenylalanine were incorporated with low affinity, and mfluoro-
tyrosine was incorporated very efficiently in vitro. m-Ftyrosine stopped proliferation of C6 cells and changed their morphology. An antibody against the C-tterminal m-F-Tyr residue was developed.