Faculty Opinions recommendation of Identification of a motif in the acetylcholine receptor beta subunit whose phosphorylation regulates rapsyn association and postsynaptic receptor localization.

1. A partially purified preparation of human placental insulin receptors was incubated with [gamma-32P]ATP in the presence or absence of insulin. The 32P-labelled insulin-receptor beta-subunits were then isolated, cleaved with trypsin followed by protease V8 and the [32P]phosphopeptides generated were analysed by thin layer electrophoresis and chromatography. This approach revealed that insulin stimulates autophosphorylation of the insulin-receptor beta-subunit in vitro on at least seven tyrosine residues distributed among three distinct domains. 2. One domain (domain 2), containing tyrosine residues 1146, 1150 and 1151 was the most rapidly phosphorylated and could be recovered as mono-, di- and triphosphorylated peptides cleaved by trypsin at Arg-1143 and either Lys-1153 or Lys-1156. Multiple phosphorylation of this domain appears to partially inhibit the cleavage at Lys-1153 by trypsin. 3. In a second domain (domain 3) containing two phosphorylated tyrosine residues at positions 1316 and 1322 the tyrosines were phosphorylated more slowly than those in domain 2. This domain is close to the C-terminus of the beta-subunit polypeptide chain. 4. At least two further tyrosine residues appeared to be phosphorylated after those in domains 2 and 3. These residues probably residue within a domain lying in close proximity to the inner face of the plasma membrane containing tyrosines 953, 960 and 972, but conclusive evidence is still required. 5. The two-dimensional thin-layer analysis employed in this study to investigate insulin-receptor phosphorylation has several advantages over previous methods based on reverse-phase chromatography. It allows greater resolution of 32P-labelled tryptic peptides and, when coupled to radioautography, is considerably more sensitive. The approach can be readily adapted to study phosphorylation of the insulin receptor within intact cells.

Download Full-text

Ligand-dependent transformation by the receptor for human granulocyte/macrophage colony-stimulating factor and tyrosine phosphorylation of the receptor beta subunit.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.90.9.3963 ◽

1993 ◽

Vol 90 (9) ◽

pp. 3963-3967 ◽

Cited By ~ 9

Author(s):

L. B. Areces ◽

M. Jucker ◽

J. A. San Miguel ◽

A. Mui ◽

A. Miyajima ◽

...

Keyword(s):

Tyrosine Phosphorylation ◽

Beta Subunit ◽

Colony Stimulating Factor ◽

Macrophage Colony Stimulating Factor ◽

Macrophage Colony ◽

Stimulating Factor ◽

Receptor Beta

Download Full-text

Amino acid sequence of the human fibronectin receptor.

The Journal of Cell Biology ◽

10.1083/jcb.105.3.1183 ◽

1987 ◽

Vol 105 (3) ◽

pp. 1183-1190 ◽

Cited By ~ 356

Author(s):

W S Argraves ◽

S Suzuki ◽

H Arai ◽

K Thompson ◽

M D Pierschbacher ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Amino Acid Sequence ◽

Calcium Binding ◽

Beta Subunit ◽

Alpha Subunit ◽

Receptor Subunit ◽

Fibronectin Receptor ◽

Adhesion Receptor ◽

Receptor Beta

The amino acid sequence deduced from cDNA of the human placental fibronectin receptor is reported. The receptor is composed of two subunits: an alpha subunit of 1,008 amino acids which is processed into two polypeptides disulfide bonded to one another, and a beta subunit of 778 amino acids. Each subunit has near its COOH terminus a hydrophobic segment. This and other sequence features suggest a structure for the receptor in which the hydrophobic segments serve as transmembrane domains anchoring each subunit to the membrane and dividing each into a large ectodomain and a short cytoplasmic domain. The alpha subunit ectodomain has five sequence elements homologous to consensus Ca2+-binding sites of several calcium-binding proteins, and the beta subunit contains a fourfold repeat strikingly rich in cysteine. The alpha subunit sequence is 46% homologous to the alpha subunit of the vitronectin receptor. The beta subunit is 44% homologous to the human platelet adhesion receptor subunit IIIa and 47% homologous to a leukocyte adhesion receptor beta subunit. The high degree of homology (85%) of the beta subunit with one of the polypeptides of a chicken adhesion receptor complex referred to as integrin complex strongly suggests that the latter polypeptide is the chicken homologue of the fibronectin receptor beta subunit. These receptor subunit homologies define a superfamily of adhesion receptors. The availability of the entire protein sequence for the fibronectin receptor will facilitate studies on the functions of these receptors.

Download Full-text