Association of tubulin carboxypeptidase activity with microtubules in living cells

CONTIN MARIA ANA; SIRONI JUAN JOSE; BARRA, HECTOR SILVIO; ARCE, CARLOS ANGEL

PORTLAND PRESS LTD

Lugar: New York; Año: 1999 vol. 339 p. 463 - 463

bstract Tubulin carboxypeptidase is the enzyme that releases the C-terminal tyrosine from alpha-tubulin, converting tyrosine-terminated (Tyr) to detyrosinated (Glu) tubulin. The present study demonstrates that this enzyme is associated with microtubules in living cells. We extracted cultured cells (COS-7) with Triton X-100 under microtubule-stabilizing conditions and found tubulin carboxypeptidase activity in the cytoskeleton fraction. We ruled out, by using several control experiments, the possibility that this result was due to contamination of the isolated cytoskeletons by non-associated proteins contained in the detergent fraction or to an artifact in vitro during the extraction procedure. The associated carboxypeptidase activity showed characteristics similar to those of brain tubulin carboxypeptidase and different from those of pancreatic carboxypeptidase A. In comparison with cultures at confluence, those at low cell density contained small (if any) amounts of carboxypeptidase