Insulin regulation of (Na/sup +/, K/sup +/)-ATPase

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5013315

Lytton, J

This thesis describes an investigation into the mechanism of insulin stimulation of (Na/sup +/,K/sup +/)=ATPase in rat adipocytes. Two molecular forms of the catalytic subunit of the enzyme were identified and denoted ..cap alpha.. and ..cap alpha..(+), due to their similarity to those isozymes previously described from rat brain. Insulin specifically stimulated the ..cap alpha..(+) form of the enzyme. The two forms of the enzyme had quite different affinities for intracellular sodium ion; insulin affected only the lower affinity of ..cap alpha..(+), shifting it toward a higher value. However, the sodium affinity of (Na/sup +/,K/sup +/)-ATPase activity in isolated membranes was equally high for both forms of the enzyme. This suggests that the difference in sodium affinity between the two forms observed in the cell is not inherent within the structure of the sodium pump, but must depend upon a selective interaction with another molecule which has been lost upon membrane isolation. Immunoprecipitation of both the catalytic subunits either from extracts of whole cells which had been labelled with (/sup 32/P) orthophosphate, or from membranes which had been labelled with ..gamma..-(/sup 32/P)ATP demonstrated that less than 1 in 100 molecules had a covalently bound phosphate insulin had no influence on this value. The amino terminal sequences of the first 4 amino acids of the catalytic subunits of both ..cap alpha.. (isolated from rat kidney) and ..cap alpha..(+) (from rat brainstem axolemma) were determined. The result shows two highly homologous but clearly different molecules. It can thus be concluded that the insulin sensitive version of the enzyme is not derived from the common ..cap alpha.. form by a post-translational modification.

• Research Organization: Harvard Univ., Boston, MA (USA)
• OSTI ID: 5013315
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ADIPOSE TISSUE
ALKALI METAL COMPOUNDS
ANIMAL CELLS
ANIMAL TISSUES
ANIMALS
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BODY
CHEMICAL ACTIVATION
CONNECTIVE TISSUE
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
ENZYME ACTIVITY
ENZYMES
FAT CELLS
HORMONES
HYDROLASES
INSULIN
ISOTOPES
LIGHT NUCLEI
MAMMALS
NUCLEI
ODD-ODD NUCLEI
PEPTIDE HORMONES
PHOSPHOHYDROLASES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
POTASSIUM COMPOUNDS
RADIOISOTOPES
RATS
RODENTS
SODIUM COMPOUNDS
SOMATIC CELLS
TISSUES
VERTEBRATES