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Biomedical subjects

E Briones

Publications and source records attributed to E Briones.

22 records · Page 2Linked to original sources
PubMed1976

NAD glycohydrolase activity in hearts with acute experimental infarction.

Myocardial ischemia was produced in dogs by occluding the descending coronary artery. NAD decreased in the ischemic tissue taken 2 h after the arterial ligature, and an equivalent amount of nicotinamide was detected instead. A further breakdown occurred when fragments of ischemic and nonischemic tissue were incubated at 37 degrees C. In contrast, NAD concentration remained unchanged for as long as 60 min in incubated fragments from normal heart. When normal tissue was homogenized, an immediate hydrolysis of NAD was observed with the formation of stoichiometric amounts of nicotinamide. An excess of nicotinamide completely inhibited the NAD degradation. The NAD glycohydrolase activity assayed in vitro was similar in normal, ischemic, and nonischemic cardiac homogenates. The conclusions are that the NAD loss in the ischemic heart is due to the tissue NAD glycohydrolase activity and that the cell disorganization provoked by the occlusion of the coronary artery seems to facilitate the reaction between the substrate and the enzyme.

Animals↗
PubMedDate not supplied

Proteins P1, P2, and P0, components of the eukaryotic ribosome stalk. New structural and functional aspects.

The eukaryoic ribosomal stalk is thought to consist of the phosphoproteins P1 and P2, which form a complex with protein PO. This complex interacts at the GTPase domain in the large subunit rRNA, overlapping the binding site of the protein L11-like eukaryotic counterpart (Saccharomyces cerevisiae protein L15 and mammalian protein L12). An unusual pool of the dephosphorylated forms of proteins P1 and P2 is detected in eukaryotic cytoplasm, and an exchange between the proteins in the pool and on the ribosome takes place during translation. Quadruply disrupted yeast strains, carrying four inactive acidic protein genes and, therefore, containing ribosomes totally depleted of acidic proteins, are viable but grow with a doubling time threefold higher than wild-type cells. The in vitro translation systems derived from these stains are active but the two-dimensional gel electrophoresis pattern of proteins expressed in vivo and in vitro is partially different. These results indicate that the P1 and P2 proteins are not essential for ribosome activity but are able to affect the translation of some specific mRNAs. Protein PO is analogous to bacterial ribosomal protein L10 but carries an additional carboxyl domain showing a high sequence homology to the acidic proteins P1 and P2, including the terminal peptide DDDMGFGLFD. Successive deletions of the PO carboxyl domain show that removal of the last 21 amino acids from the PO carboxyl domain only slightly affects the ribosome activity in a wild-type genetic background; however, the same deletion is lethal in a quadruple disruptant deprived of acidic P1/P2 proteins. Additional deletions affect the interaction of PO with the P1 and P2 proteins and with the rRNA. The experimental data available support the implication of the eukaryotic stalk components in some regulatory process that modulates the ribosomal activity.

Amino Acid Sequence↗