Biomedical subjects

G Guidotti

Publications and source records attributed to G Guidotti.

At least 73 records · Page 4Linked to original sources

PubMed1978

Vanadate inhibits the red cell (Na+, K+) ATPase from the cytoplasmic side.

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Anions↗

PubMed1977

Vanadate is a potent (Na,K)-ATPase inhibitor found in ATP derived from muscle.

A potent (Na,K)-ATPase inhibitor purified from "Sigma Grade* ATP has been identified as vanadium using electron probe microanalysis and confirmed by microwave-induced emission spectroscopy and electron paramagnetic resonance spectroscopy. Sodium orthovanadate (Na3 VO4) is identical with the purified inhibitor with respect to ultraviolet absorbance, migration on thin layer chromatography, and inhibition of (Na,K)-ATPase. The (Na,K)-ATPase is in-inhibited 50% by 40 nM Na3 VO4 under optimal conditions (28 mM Mg2+) and the inhibition is 100% reversible by millimolar concentrations of norepinephrine. The physiological significance of this inhibition is discussed in relation to vanadium concentrations in vivo.

Adenosine Triphosphatases↗

PubMed1977

The structure of intrinsic membrane proteins.

Intrinsic membrane proteins are embedded in the lipid bilayer so that the polypeptides come in contact with the non-polar region of the bilayer. There are two major types of intrinsic proteins: those with most of their mass outside the cytoplasm (Type I) and those with most of their mass inside the cytoplasm (Type II). In the latter group are the membrane transport systems. The anion exchange system of the human erythrocyte is a dimer of band 3 polypeptides. These polypeptides span the bilary, have most of their mass in the cytoplasm, and are glycosylated. About 20-25% of the polypeptide, however, is in the bilayer. Arguments are presented to support the view that the intramembrane segments of the protein are alpha-helical and that the major protein-protein interactions between the subunits are in the cytoplasmic portion of the protein.

Biological Transport, Active↗

PubMed1975

A membrane protein from human erythrocytes involved in anion exchange.

Phosphate transport across the membrane of human erythrocytes, at pH 6.42, is a saturable process with an external Km of 80 mM and a Vmax of 2.8 mmol per liter of red cells per min. Transport is inhibited in a reversible manner by the sulfanilate anion and in an irreversible manner by the isothiocyanate derivative of the sulfanilate anion. This reagent reacts with only one membrane protein. When 300,000 molecules of reagent per cell are covalently attached to protein, transport is completely inhibited. This transport protein is a glycoprotein, it belongs to the general class designated as component a by Bretscher, and it therefore spans the bilayer. Transport does not involve movement of the protein around an axis parallel to the plane of the membrane.

Amines↗

PubMed1974