JBC, Vol. 254, Issue 22, 11505-11510, Nov, 1979
Tubulin tyrosylation in vivo and changes accompanying differentiation of cultured neuroblastoma-glioma hybrid cells
J. Nath and M. Flavin
Changes in a posttranslational modification of tubulin, which accompany
differentiation, have been studied in neuroblastoma-glioma hybrid cultured
cells. The modification consists of the reversible enzymatic addition of a
tyrosine to the COOH terminus of the alpha chain. Cytoplasmic tubulin
purified from undifferentiated cells resembled that from adult mammalian
brain in that half was in a form which can not accept tyrosine; of the
remainder, which is a substrate for tubulin-tyrosine ligase, a higher
proportion had COOH-terminal tyrosine. In the tubulin from differentiated
cells, in which there had been extensive assembly of axonal microtubules
from a preformed pool of subunits, the nonsubstrate tubulin was almost
entirely replaced by the species with COOH-terminal tyrosine. In living
cells, in the absence of protein synthesis, there was fixation of labeled
tyrosine into cytoplasmic alpha chains which was extensive enough to be
consistent with turnover, during the course of an hour, of the pre-existing
COOH-terminal tyrosine. The alpha chain in the particulate fraction of the
cells was comparably labeled, along with some unidentified low molecular
weight components.
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