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C A Arce

Publications and source records attributed to C A Arce.

28 records · Page 2Linked to original sources
PubMed1980

Total tubulin and its aminoacylated and non-aminoacylated forms during the development of rat brain.

The amount of total tubulin in the soluble fraction of rat brain was measured by a method based on the purification of tubulin previously labeled by incorporation of [14C]tyrosine in the C terminus of its alpha-chain. The tubulin content decreased from 2.01 to 1.30 nmol/mg protein when the animals passed from 4 to 30 days of age and then remained practically constant. The amounts of aminoacylated and non-aminoacylated tubulin present in the soluble brain extracts were determined from the incorporation of [14C]tyrosine into the free acceptor sites of tubulin preparations, that were preincubated without carboxypeptidase A or with this enzyme to eliminate tyrosine and phenylalanine from the C terminus of the alpha-chain of tubulin. The values obtained were corrected for the inactivation of tubulin to accept [14C]tyrosine that occurred during the isolation and incubation of the soluble fractions. The ratio non-aminoacylated/aminoacylated tubulin increased from 1.62 +/- 0.03 in the 4-day-old rats to 2.11 +/- 0.17 in the 120-day-old rats. The aminoacylatable tubulin, that is the sum of aminoacylated plus non-aminoacylated tubulin, decreased from 1.71 to 0.75 nmol/mg protein from 4-day-old to 30-day-old rats respectively and then remained practically constant. The amount of aminoacylatable tubulin is lower than that of total soluble tubulin. Therefore there is a fraction of tubulin that is unable to accept tyrosine. This non-aminoacylatable tubulin fraction increases with the age of the animal so that in the 120-day-old rats this tubulin species accounts for 48% of the total soluble tubulin.

Aging↗
PubMed1975

Incorporation of L-tyrosine, L-phenylalanine and L-3,4-dihydroxyphenylalanine as single units into rat brain tubulin.

The product of the incorporation of [14C]tyrosine as single unit into a protein of the soluble fraction of rat brain homogenate was purified by following a procedure used to purify tubulin. Sodium dodecylsulphate-polyacrylamide gel electrophoresis of the purified material showed a single protein band containing all the radioactivity. Purification data indicate that this protein accounts for 10.2% of the total protein of the supernatant fraction. This is in good agreement with the amount found for tubulin by the [3H]colchicine-binding method (10.5% of the total protein). The incorporated [14C]-tyrosine was found in the alpha-subunit of tubulin. Protein labelled with [3H]colchicine and [14C]tyrosine was precipatated with vinblastine sulphate and the radioactivity of 3H and that of 14C were quantitatively recovered in the precipitate (98%). Sodium dodecylsulphate-polyacrylamide gel electrophoresis of the vinblastine precipitate showed that the 14C radioactivity moved with the tubulin band. Results obtained in experiments with phenylalanine and 3,4-dihydroxyphenylalanine were identical to those obtained for tyrosine. Bineing of colchicine did not interfere with the incorporation of tyrosine. About 30% of tubulin from rat brain supernatant fraction can incorporate tyrosine as single unit.

Animals↗
PubMed1975

The reciprocal exclusion by L-dopa (L-3,4-dihydroxyphenylalanine) and L-tyrosine of their incorporation as single units into a soluble rat brain protein.

Several compounds, structurally and metabolically related to phenylalanine and tyrosine, were tested for their effects on the incorporations of phenylalanine and tyrosine as single units into a protein of the soluble subcellular fraction of rat brain. Of the compounds tested, only L-dopa (L-3,4-dihydroxyphenylalanine) inhibited these incorporations. Further, L-dopa was incorporated into a protein of the same fraction in such a way that it excluded the incorporation of tyrosine as a single unit. Conversely, tyrosine inhibited and excluded the incorporation of L-dopa. The incorporation of L-dopa required ATP (apparent Km = 0.23mM), KCl (apparent Km = 20mM) and MgCl2 (optimal concentration range, 5-16mM). These requirements were similar to those previously determined for the incorporation of tyrosine and phenylalanine. The inactivation rate of the enzymic systems for L-tyrosine and L-dopa incorporations, when kept at 37 degrees C, was the same for both amino acids (half-life = 80 min). It is suggested that the acceptor for the incorporation of dopa is the same as that for the incorporation of tyrosine.

Adenosine Triphosphate↗