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Epidermal growth factor dependent phosphorylation of a 35-kilodalton protein in placental membranes

Journal Article · · Biochemistry; (United States)
DOI:https://doi.org/10.1021/bi00378a026· OSTI ID:6524785
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In human placental membranes isolated in the presence of ethylenediaminetetraacetic acid (EDTA), epidermal growth factor (EGF) stimulated the )..gamma..-/sup 32/P)ATP-dependent phosphorylation of tyrosine residues on the 170-kilodalton (kDa) EGF receptor and on a 35-kDa protein. The initial rate of phosphorylation of these proteins in the presence of EGF was 5.2 and 3.5 nmol of phosphate min/sup -1/ (mg of receptor protein)/sup -1/, and this was approximately 10- and 6-fold higher than the basal rate, respectively. Half-maximal phosphorylation of both proteins occurred at about 2.5 nM EGF. In the presence of rho-nitrophenyl phosphate, EGF stimulated the phosphorylation of the 35-kDa protein but not the EGF receptor, suggesting that hormone-stimulated autophosphorylation of the receptor/kinase was not required for kinase activation. The 35-kDa protein exists in two forms: (1) 35K/sup eluate/, which was associated with the membrane in the presence of Ca/sup 2 +/ but was eluted with EDTA, and (2) 35K/sup memb/, which was not eluted from membranes with EDTA. Both forms were immunologically related to a 35-kDa protein previously isolated from A431 cells. Antiserum against the 35-kDa protein also reacted with a protein with an apparent size of 66 kDa that was phosphorylated in an EGF-dependent manner. These results suggest that the nonphosphorylated form of the 35-kDa protein associates with the membrane in a Ca/sup 2 +/-independent manner, while the phosphorylated form requires Ca/sup 2 +/ for membrane association. The phosphorylated form associated with phospholipid liposomes in a Ca/sup 2 +/-dependent manner with half-maximum association occurring at approximately 10 ..mu..M Ca/sup 2 +/.
Research Organization:
Univ. of California, Irvine
OSTI ID:
6524785
Journal Information:
Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:4; ISSN BICHA
Country of Publication:
United States
Language:
English

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Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINO ACIDS
ANIMAL GROWTH
ANIMAL TISSUES
ATP
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMISTRY
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHELATING AGENTS
CHEMICAL REACTIONS
CHEMISTRY
DAYS LIVING RADIOISOTOPES
EDTA
ELECTRON CAPTURE RADIOISOTOPES
ELECTROPHORESIS
EPIDERMIS
EPITHELIUM
FETAL MEMBRANES
GROWTH
HYDROXY ACIDS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LIPOSOMES
MEMBRANES
MOLECULAR STRUCTURE
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORYLATION
PLACENTA
PROTEINS
RADIOISOTOPES
RADIORECEPTOR ASSAY
SKIN
TISSUES
TRACER TECHNIQUES
TYROSINE