Properties of a non-specific nucleotidase in the membrane of rabbit red cells.

A non-specific nucleotidase was found in rabbit red blood cell membrane and, using 5'-AMP as substrate, several kinetic parameters for the enzyme were determined. Rabbit red cell ghosts catalyzed the hydrolysis of a wide spectrum of nucleoside 5'-, 3'- and 2'-monophosphates and a limited number of non-nucleotide substrates. All these activities were heat inactivated at the same rate, suggesting that they are the result of catalysis by the same enzyme.

Human red blood cell membrane adenylate cyclase in sickle-cell disease.

The basal and the NaF-stimulated activities of human red blood cell membrane adenylate cyclase were found to be 5.3 +/- 0.8 (SE) and 219 +/- 76 (SE) pmol .

Protein kinase and adenylate cyclase of erythrocyte membrane from patients with Duchenne muscular dystrophy.

In freshly prepared erythrocyte membranes from normal individuals and from patients with Duchenne progressive muscular dystrophy the endogenous protein kinase and the cAMP stimulated phosphorylation was identical for the three main 32P proteins including spectrin (protein band II). Another enzyme, adenylate cyclase, was found unchanged. Altered protein kinase and adenylate cyclase has been reported in this disorder.

Absence of any detectable activity of the membrane marker enzyme 5'-nucleotidase in human red blood cells.

We have investigated in human red blood cell membranes the presence of a 5'-nucleotidase, which is considered a general marker of plasma membranes. No activity was detectable with a highly sensitive colorimetric method. This absence is not due to the rapid decline of enzyme activity in the course of red cell ageing, nor to its release during membrane preparation; nor is it due to substrate accessibility hindrance to the active center of the enzyme.

[The constituents of the red cell membrane (author's transl)].

Erythrocyte plasma membrane consists of lipids, proteins and carbohydrates. The major lipids are phosphoglycerolipids which are amphiphatic molecules and which are responsible for the double layer structure of the membrane. Both membrane leaflets are fluid structures.

The enzymes of the red blood cell plasma membrane.

Red blood cell plasma membranes contain a number of enzymes: ATPases, anion transport protein, glyceraldehyde 3-phosphate dehydrogenase, protein kinases, adenylate cyclase, acetylcholinesterase. Most of them are tightly bound to the membrane and are present in small amounts. As a result, structural characterization of erythrocyte membrane enzymes has not yet been successful.

Characterization of a rat liver factor that inhibits initiation of protein synthesis in rabbit reticulocyte lysates.

Protein synthesis in rabbit reticulocytes and their lysates is regulated by heme. In heme-deficient reticulocyte lysates, protein synthesis proceeds at the initial rate for several minutes and then declines abruptly. Inhibition of protein synthesis is due to the activation of a heme-regulated translational inhibitor (HRI) which blocks the initiation of protein synthesis.

[Erythrocyte membrane proteins].

Proteins are important constituents of the red blood cell plasma membrane. Several important breakthroughs have occurred in their analysis over the past few years. SDS-polyacrylamide gel electrophoresis lead to the separation of the major proteins and glycoproteins.

Regulation of protein synthesis in rabbit reticulocyte lysates: characteristics of inhibition of protein synthesis by a translational inhibitor from heme-deficient lysates and its relationship to the initiation factor which binds Met-tRNAf.

In heme-deficient reticulocyte lysates a translational inhibitor which regulates protein synthesis is formed or activated. To define the mechanism of action of the translational inhibitor (RI), RI was partially purified. We have utilized the isolated RI to examine its relationship to the translational inhibitor formed in situ in heme-deficiency, some quantitative aspects of inhibition of protein synthesis, and the relationship of RI concentration to the initiation factor (IF-MP) which forms a ternary complex with Met-tRNAf and GTP (IF-MP-Met-tRNAf-GTP).

Immunogenic properties of eukaryotic ribosomal proteins.

Pure rat, chicken and kidney bean ribosomal proteins are immunogenic in the rabbit as tested by the Ouchterlony double diffusion technique. On the other hand, we were unable to raise antibodies to rabbit ribosomal proteins in the guinea pig. Rabbit ribosomal proteins are not autoimmunogenic.

Eukaryotic ribosomal proteins. Molecular weights of proteins from rabbit liver subunits.

The molecular weights of the proteins from rabbit liver ribosomal 40 S and 60 S subunits were determined after preliminary separation of these proteins by two-dimensional electrophoresis: each spot present in the polyacrylamide slab was cut off, eluted and rerun in a SDS one-dimensional polyacrylamide gel. The molecular weights range from 9,000 to 35,000 with a number-average molecular weight of 19,600 for the 40 S proteins, and from 9,400 to 52,000 with a number-average molecular weight of 23,600 for 60 S proteins.