Threonine 1336 of the human insulin receptor is a major target for phosphorylation by protein kinase C

The ability of tumor-promoting phorbol diesters to inhibit both insulin receptor tyrosine kinase activity and its intracellular signaling correlates with the phosphorylation of the insulin receptor beta subunit on serine and threonine residues. In the present studies, mouse 3T3 fibroblasts transfected with a human insulin receptor cDNA and expressing greater than one million of these receptors per cell were labeled with [32P]phosphate and treated with or without 100 nM 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA). Phosphorylated insulin receptors were immunoprecipitated and digested with trypsin. Alternatively, insulin receptors affinity purified from human term placenta were phosphorylated by protein kinase C prior to trypsin digestion of the 32P-labeled beta subunit. Analysis of the tryptic phosphopeptides from both the in vivo and in vitro labeled receptors by reversed-phase HPLC and two-dimensional thin-layer separation revealed that PMA and protein kinase C enhanced the phosphorylation of a peptide with identical chromatographic properties. Partial hydrolysis and radiosequence analysis of the phosphopeptide derived from insulin receptor phosphorylated by protein kinase C indicated that the phosphorylation of this tryptic peptide occurred specifically on a threonine, three amino acids from the amino terminus of the tryptic fragment. Comparison of these data with the known, deduced receptor sequence suggested that the receptor-derived tryptic phosphopeptide might be Ile-Leu-Thr(P)-Leu-Pro-Arg. Comigration of a phosphorylated synthetic peptide containing this sequence with the receptor-derived phosphopeptide confirmed the identity of the tryptic fragment. The phosphorylation site corresponds to threonine 1336 in the human insulin receptor beta subunit.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cloning of the nucleic acid-binding domain of the rat HnRNP C-type protein

A cDNA encoding the nucleic acid-binding domain of the hnRNP C-type protein has been cloned by DNA-affinity screening of pituitary-derived expression libraries. An analysis revealed sequence identity with the human C-type cDNA and demonstrated the presence of a peptide sequence contained within the single-stranded DNA-binding protein, UP2, which was absent from the human cDNA. Structural analysis of the protein encoded by the rat cDNA demonstrated a net charge of +15 with 14.56% and 6.33% lysines and arginines, respectively, and an amino acid sequence that is consistent with an extensive helix-loop-helix-turn-helix structure.     

DISCOVERY OF LATE CRETACEOUS PALYNOFLORA FROM FILDES PENINSULA, KING GEORGE ISLAND, ANTARCTICA AND ITS SIGNIFICANCE

This paper makes an analysis and study on altogether 8 palyniferous samples from the volcano-sedimentary rock series in the Half Three Point area of the Fildes Peninsula, King George Island, Antarctica, the rock series being grey tuffaceous siltstone in lithological characters, about 5m in thickness. Only after making a number of analyses, could we find the relatively abundant sporopollen fossils from 4 samples (Nos. GWP 4—7). But the fossils are poorly preserved, and most of them can hardly be identifi...     

A case of D13 ring chromosome

Summary A case of D ring chromosome identified with trypsin banding as a 13 with loss of the bands p12 and q34 is reported. The clinical features characteristically associated with the loss of these specific segments were present.     

An attempt to determine lipid peroxides with polyethylene glycol-modified hemin

Hemin, having two carboxyl groups, was coupled with alpha-(3-aminopropyl)-omega-methoxypoly(oxyethylene) through the acid-amide bond formed with carbodiimide. The modified hemin catalyzed the peroxidase reaction in 1,1,1-trichloroethane using benzoyl peroxide or peroxides in unsaturated fatty acids as the hydrogen acceptor and leuco crystal violet as the hydrogen donor. A basic study on quantitative microanalysis of the lipid peroxides was attempted.