Phosphorylation and proteolysis of HMGCoA reductase

Conference · Fri May 01 00:00:00 EDT 1987 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:6286000

Parker, R A; Lanier, T L; Miller, S J; Gibson, D M

The phosphorylation of rat liver microsomal 97 kDa HMGCoA reductase (HMGR) was examined by immunoprecipitation and SDS-PAGE using antibodies to 53 kDa HMGR. MgATP preincubation decreased expressed HMGR activity from 10.1 +/- 2.4 to 0.81 +/- 0.2 U/mg. Concomitant incorporation of TSP from el-TSP-ATP into 97 kDa HMGR protein was observed. Competitive antibody binding by affinity-purified 53 kDa HMGR showed that the 97 kDa TSP band was authentic HMGR. HMGR was reactivated and the TSP label was removed by protein phosphatase in a concentration-dependent manner: the increase in expressed/total activity ratio (E/T) correlated linearly with a decrease in 97 kDa TSP. Therefore, the E/T ratio provides a valid index of the phosphorylation state of microsomal 97 kDa HMGR. Protease cleavage patterns of HMGR mass and TSP were compared using calpain: a 52-56 kDa doublet of HMGR mass was observed in immunoblots under conditions in which only the 56 kDa band contained TSP. Further proteolysis decreased the TSP label as the 52 kDa mass product increased. The data suggest that the major phosphorylation site in 97 kDa HMGR lies between two main calpain cleavage sites in the linker region joining the cytoplasmic domain to the membrane-spanning domain of the native enzyme.

• Research Organization: Indiana Univ. School of Medicine, Indianapolis
• OSTI ID: 6286000
• Report Number(s): CONF-870644-; TRN: 87-028656
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
OXIDOREDUCTASES
PHOSPHORYLATION
PROTEOLYSIS
ATP
CPB
ELECTROPHORESIS
ENZYME ACTIVITY
LIVER
MICROSOMES
PHOSPHORUS 32
RATS
TRACER TECHNIQUES
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CELL CONSTITUENTS
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DIGESTIVE SYSTEM
ENZYMES
GLANDS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MAMMALS
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
PHOSPHORUS ISOTOPES
RADIOISOTOPES
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques