Epidermal growth factor (urogastrone)-mediated phosphorylation of a 35-kDa substrate in human placental membranes: relationship to the. beta. subunit of the guanine nucleotide regulatory complex

Journal Article · Wed Jan 01 04:00:00 EST 1986 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.83.2.236· OSTI ID:6220517

Valentine-Braun, K A; Northup, J K; Hollenberg, M D

The authors have identified a component of about 35 kDa (pp35), present in human placental membrane preparations, that is a substrate for epidermal growth factor urogastrone) (EGF(Uro))-mediated phosphorylation. The EGF(Uro)-stimulated phosphorylation of pp35 was calcium-dependent and was markedly enhanced in membranes prepared in the presence (but not in the absence) of calcium. The (/sup 32/P)-phosphate incorporated into pp35 in the presence of EGF(Uro) was alkali-stable and was present as O/sup 4/-phosphotyrosine. Under identical conditions, insulin did not stimulate pp35 phosphorylation. Either in its native or in its phosphorylated form, pp35 could be released from the membranes in the presence of calcium-chelating agents (EDTA/EGTA); and EGF(Uro)-stimulated phosphorylation was reconstituted by adding back EDTA/EGTA eluates to EDTA/EGTA-washed membranes in the presence of calcium. The properties of pp35 were similar if not identical to those of ..beta..-35, a 35-kDa polypeptide similar to the ..beta.. subunit of the guanine nucleotide-binding oligomers that stimulate (G/sub s/) or inhibit (G/sub i/) the adenylate cyclase system. In contrast, the addition of ..beta.. subunits derived from rabbit liver G/sub i/ or bovine transducin did not result in phosphorylation of a 35-kDa substrate in the reconstituted system. They conclude that the human placental pp35 substrate likely represents the placental equivalent of the ..beta..-35 protein. The data point to a possible link between those receptors involved in growth-factor action and the regulatory systems that utilize GTP-binding proteins as transducing elements.

• Research Organization: Univ. of Calgary, Alberta
• OSTI ID: 6220517
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 83:2; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METAL COMPOUNDS
ANIMAL TISSUES
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMISTRY
BODY
CALCIUM COMPOUNDS
CHEMICAL REACTIONS
CHEMISTRY
DAYS LIVING RADIOISOTOPES
ENZYMES
EPIDERMIS
EPITHELIUM
FETAL MEMBRANES
GROWTH
HORMONES
ISOTOPES
LABELLING
LIGHT NUCLEI
MAMMALS
MAN
MEMBRANE PROTEINS
MEMBRANES
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHORYLATION
PHOSPHOTRANSFERASES
PITUITARY HORMONES
PLACENTA
PRIMATES
PROTEINS
RADIOISOTOPES
RECEPTORS
SKIN
STH
TISSUES
TRANSFERASES
VERTEBRATES