PubMed Health⌕ Search

Biomedical subjects

J L Saborío

Publications and source records attributed to J L Saborío.

9 recordsLinked to original sources
PubMed1985

Purification and characterization of GP-55, a protein associated with actin-based cytoplasmic gels derived from brain tissue.

Incubation of rat brain cytoplasmic extracts results in the formation of three-dimensional gels that can be collapsed by low-speed centrifugation. Electrophoresis in polyacrylamide gels indicate that these cytoplasmic gels are composed of actin and several associated proteins. Among the latter we have identified a component with an apparent molecular mass of 55,000 daltons. The results of two-dimensional electrophoresis, peptide mapping, and in vivo labeling experiments with [35S]methionine, indicate that the 55-kDa protein is composed of two different gene products we have named alpha and beta; a third polypeptide, named beta', probably derives from the beta polypeptide as a result of some posttranslational modification(s). These three polypeptides, which have the same molecular weight but different isoelectric points, are present in a rather pure preparation of the 55-kDa protein, obtained from cytoplasmic gels by ion-exchange chromatography. In vitro, purified 55-kDa protein interacts in a specific manner with F-actin, as shown by viscosimetry and electron microscopy, leading to the formation of a complex network of cross-linked microfilament bundles. The results of immunofluorescence experiments indicate that the 55-kDa protein is located intracellularly in structures belonging to the Golgi apparatus, and that it is not only present in every type of rat cell tested but also in primary cultures of chick embryo neurons. Based on its intracellular location, we have named the 55-kDa protein as Golgi Protein-55 (GP-55).

Actins↗
PubMed1984

Actin-based gelation of cytoplasmic extracts from brain tissue.

Incubation of rat brain cytoplasmic extracts under the conditions described in this paper results in the formation of three-dimensional gels. Ultrastructurally, these gels correspond to complex supramolecular structures formed by single microfilaments and by microfilament bundles. Analysis of protein composition indicates that cytoplasmic gels are composed of actin and several associated proteins. Among the latter class of components, we have identified polypeptides with molecular weights of 55,000 (55K), 140,000 (140K), and a set of two or three polypeptides with molecular weights in the range of 235,000-245,000 (235-245K). The 55K and 140K components do not seem to correspond to any previously identified actin-associated proteins, while the 235-245K polypeptides may correspond to the protein known as fodrin.

Actins↗
PubMed1982

Separation of the mRNAs coding for different forms of chick embryo gizzard tropomyosin.

The fractionation of gizzard tropomyosin from 17-day-old chick embryos by electrophoresis in polyacrylamide gels indicates that this protein is composed of three different polypeptides that were designated as alpha, beta, and gamma. Each one of these polypeptides is resolved into two components with different isoelectric points when tropomyosin is fractionated by two-dimensional electrophoresis; the major components were designated as tropomyosins alpha 1, beta 1, and gamma 1 and the minor ones as tropomyosins alpha 2, beta 2, and gamma 2. The results of in vitro translation of gizzard RNA indicate that only tropomyosins alpha 1, beta 1, and gamma 1 are synthesized in the cell-free system. A partial separation of the mRNAs coding for tropomyosins alpha 1 and gamma 1 was obtained by fractionation of gizzard RNA by zonal centrifugation in sucrose gradients. Altogether these results indicate that in gizzard tissue from 17-day-old chick embryos three genes coding for different forms of tropomyosin are expressed.

Animals↗
PubMed1982

Phosphorylated and unphosphorylated forms of cardiac tropomyosin.

Cardiac tropomyosin from 20-day-old chick embryos is composed of three different polypeptides with the same molecular weight but different isoelectric points. These polypeptides, which are designated as alpha 1, alpha 2, and alpha 3, have identical peptide maps. In vitro, however, only polypeptide alpha 1 is synthesized in a reticulocyte lysate programmed with cardiac RNA. These results, together with the observations indicating that tropomyosin alpha 2 corresponds to a phosphorylated polypeptide, suggest that only tropomyosin alpha 1 corresponds to a primary translational product and that forms alpha 2 and alpha 3 are derived from alpha 1 as a consequence of posttranslational modifications.

Animals↗
PubMed1981

Brain actin synthesized in vitro undergoes two different and sequential posttranslational modifications.

The have studied the posttranslational processing of actin molecules synthesized in a cell-free system. The results of these experiments indicate that during the in vitro synthesis of the actins from rat brain the primary translational products undergo two different and sequential posttranslational modifications. These modifications are accompanied by slight changes in the isoelectric points of the proteins and can be detected by isoelectric focusing analysis. The same posttranslational modifications can be detected during the in vitro synthesis of chick embryo skeletal muscle actin. The evidence presented suggest that the first posttranslational modification may correspond to the methylation of a histidine residue, and the second modification most likely corresponds to the acetylation of the NH(2)-terminal amino acid residues of actin molecules.

Acetyl Coenzyme A↗
PubMed1980

Heterogeneity of glutamine synthetase polypeptides in Neurospora crassa.

Purified preparations of Neurospora crassa glutamine synthetase contain two nonidentical polypeptides that can be separated by acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and 7 M urea. These polypeptides are synthesized both in vivo and in a heterologous cell-free protein-synthesizing system. The data presented indicate that both polypeptides contain an active site for glutamine synthetase activity and suggest that there is not a precursor-product relationship between them.

Glutamate-Ammonia Ligase↗