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The distribution of a novel pituitary protein (7B2) was determined in the gastrointestinal tract and pancreas of four mammalian species (man, pig, guinea pig, and rat) by a specific radioimmunoassay. The highest concentrations of cross-reacting immunoreactive 7B2 (IR-7B2) were observed in the pancreas and the proximal gut (antrum or duodenum). While the intestinal concentrations varied widely among species, pancreatic IR-7B2 concentrations appeared to be similar in all four species. In the rat, pancreatic islets were found to contain high concentrations of IR-7B2 (5.73 +/- 0.14 fmol/islet, mean +/- SEM). Neonatal capsaicin treatment and enteric nerve section did not affect the concentrations of IR-7B2 in the rat intestine. Layer separation of human gut showed that IR-7B2 is mainly (71 +/- 8%) present in the epithelial fraction. Chromatographic analysis of intestinal and pancreatic extracts from the four species on Sephadex G-100 showed the presence of two immunoreactive peaks at Kav 0.3 and 0.6, but there were both inter- and intraspecies variations in the proportions of the larger and smaller molecular forms.
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PMID:Distribution of a novel pituitary protein (7B2) in mammalian gastrointestinal tract and pancreas. 328 56

7B2 is a protein originally isolated from pituitary, which has been shown to be present in the central nervous system and in certain peripheral tissues, with very high concentrations in pancreatic islets. Endocrine and nonendocrine tumors from 185 patients were investigated by RIA for the presence of immunoreactive pituitary protein 7B2. The highest mean concentration of 7B2 immunoreactivity was found in insulinomas [452 +/- 174 (+/- SEM) pmol/g wet wt tissue; n = 16], which was significantly higher than the concentration in normal adult pancreatic tissue (28.3 +/- 4.4 pmol/g; n = 7). High concentrations of 7B2 immunoreactivity also were found in other endocrine tumors. The cellular localization of 7B2 was studied in normal pancreas, pancreas with hyperplastic islets, and endocrine tumors. 7B2 immunoreactivity was localized to B-cells in the normal pancreas and to variable proportions of cells in islet cell hyperplasias, B-cell tumors, and pheochromocytomas. Plasma concentrations of 7B2 immunoreactivity also were determined in 255 patients with established diagnoses of endocrine or nonendocrine tumors. The proportion of patients with elevated plasma concentrations (arbitrarily set at more than 4 SD above the mean) were 42 of 72 with pancreatic islet cell tumors, 7 of 11 with midgut carcinoid tumors, and 5 of 13 with medullary carcinomas of the thyroid. Especially high values were found in patients with glucagonomas (14 of 20), vipomas (12 of 13), and pancreatic polypeptide-producing tumors (5 of 6). Thus, 7B2 immunoreactivity is produced by a variety of different tumors and may serve as a tumor marker, especially in patients with certain pancreatic islet tumors.
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PMID:Production of pituitary protein 7B2 immunoreactivity by endocrine tumors and its possible diagnostic value. 352 2

Using a specific radioimmunoassay, we measured concentrations of plasma 7B2 (a novel pituitary polypeptide) immunoreactivity (7B2-IR) in normal human subjects, patients with chronic renal failure and those with liver cirrhosis. Mean (+/- SEM) values of plasma 7B2-IR in normal healthy men and women were 55.8 +/- 1.2 pg/ml (n = 266) and 56.1 +/- 0.9 pg/ml (n = 408), respectively. The elevation of plasma 7B2-IR showed a relationship with age of the subjects, in both men (r = 0.39, t = 6.86, p less than 0.001) and women (r = 0.35, t = 7.44, p less than 0.001). Plasma 7B2-IR concentrations were elevated in patients with chronic renal failure (536 +/- 45 pg/ml, Mean +/- SEM, n = 10) as well as those in liver cirrhosis (95 +/- 10 pg/ml, Mean +/- SEM, n = 15) compared to values in normal subjects, suggesting that 7B2 is mainly eliminated through the kidney and is partly metabolized in the liver.
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PMID:Age-related change in plasma concentration of 7B2 (a novel pituitary polypeptide) in normal humans. 361 60

We observed the presence of the novel pituitary protein "7B2" and its release in the bovine adrenal medulla. The 7B2 concentration (mean +/- SEM) in extracts of the bovine adrenal medulla was 952 +/- 155 pg/mg tissue (n = 6). 7B2 was distributed in the chromaffin granule fraction prepared from the bovine adrenal medulla and was released by high K+ and/or nicotine from cultured cells of the bovine adrenal medulla. Co-release of 7B2 with catecholamine induced by nicotine from the cultured bovine chromaffin cells was also observed. In an analysis of the bovine adrenal medulla chromaffin granule fraction on gel permeation chromatography, there was a major peak with an apparent molecular weight of 45,000, whereas a major peak with an apparent molecular weight of 20,000 was found in that on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On reverse-phase HPLC, a major peak with a retention time of 35 min was observed in the bovine chromaffin granule fraction and in the bovine anterior pituitary extract. These findings indicate that 7B2 is a secretory protein in the bovine adrenal medulla. The possibility that 7B2 might be released with catecholamine, possibly in response to stress, warrants investigation.
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PMID:Presence of the novel pituitary protein "7B2" in bovine chromaffin granules: possible co-release of 7B2 and catecholamine as induced by nicotine. 368 Dec 97

A sensitive and specific radioimmunoassay (RIA) was developed for a novel pituitary protein that we recently isolated from human and porcine pituitary gland and designated 7B2. By employing this RIA, we were able to detect and assay this novel protein in different rat tissue extracts. The concentrations of 7B2 in rat anterior pituitary lobe, neurointermediate lobe, hypothalamus, adrenal medulla and thyroid gland were 10,400 +/- 804; 6,190 +/- 908; 773 +/- 50; 697 +/- 83 and 1,368 +/- 116 pg/mg tissue (wet weight, n = 10, mean +/- SEM), respectively. However, the concentrations of 7B2 were lower than 30 pg/mg tissue in extracts of pancreas, ileum and colon, and were below the sensitivity of the RIA in extracts of liver, kidney, spleen, lung, adrenal cortex and testis. Gel permeation chromatography of extracts of anterior pituitary lobe, neurointermediate lobe, hypothalamus, adrenal medulla and thyroid gland on Sephadex G-100 revealed that most of the immunoreactive (Ir)-7B2 has an apparent molecular weight of 45,000-50,000. Subsequent dissociation of this Ir-7B2 by polyacrylamide gel electrophoresis containing sodium dodecyl sulfate (SDS) yielded an Ir-7B2 with an apparent molecular weight of around 19,000. In addition, high K+ concentration (50 mM) induced the release of Ir-7B2 from cultured cells of both rat anterior pituitary and neurointermediate lobe. Finally, Ir-7B2 was detected in the neurosecretory granule fraction prepared from porcine neurointermediate lobe. These results indicate that 7B2 may be a novel secretory protein in the pituitary gland.
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PMID:Tissue distribution and molecular forms of a novel pituitary protein in the rat. 651 32

Ubiquitin is often implicated as a specific tag for protein degradation via the ubiquitin system although only a limited number of physiological proteins have been shown to be degraded in their native tissues via this pathway in vivo. Ubiquitin may also, however, have other functions of a regulatory nature (non-catabolic ubiquitylation). The ubiquitylation of calmodulin appears to fall into this category. Ubiquitin is linked to free calmodulin in the presence of the second messenger Ca2+ by the enzyme ubiquitin-calmodulin ligase (uCaM synthetase: EC 6.3.2.21) and there is no evidence that this step is followed by degradation of calmodulin via the ATP-dependent 26-S protease. Due to a lack of natural substrates and sufficient tissue material, only a few components of the ubiquitin system have been obtained in truly homogeneous form from reticulocytes. We therefore decided to attempt this for the calmodulin ligase. The enzymic components of the uCaM synthetase system copurified over several steps and could be highly enriched by a novel sample displacement technique on an ion-exchange resin. A fractionation of the synthetase components by affinity chromatography on ubiquitin-Sepharose and calmodulin-Sepharose yielded two essentially inactive components: a ubiquitin-Sepharose binding fraction (uCaM Syn-F1) and a calmodulin-Sepharose binding fraction (uCaM Syn-F2). The full activity of uCaM synthetase can be reconstituted when these two fractions are reunited. uCaM Syn-F1 could then be separated from all other enzymes of ubiquitin metabolism and, employing the second component with the natural substrate calmodulin, could be purified over 3500-fold to homogeneity. The ability to catalyze its own thiol labile ubiquitylation identified it as a member of the ubiquitin-activating enzyme family (E1). The homogeneous preparation contained a single protein of molecular mass 213 +/- 21 kDa (mean +/- SEM) as determined by gel filtration. The molecular mass of the monomer was determined by electrospray ion mass spectrometry to 112,140 +/- 47 Da (mean +/- SD). N-terminal sequence analysis (20 amino acids) led to a single N-terminal peptide beginning at residue 57 of the known rabbit cDNA sequence. No ragged N-terminus was detected, as would be expected by the action of an aminopeptidase or other peptidases of low specificity. The monomer molecular mass calculated from the cDNA sequence (Arg57-Arg1058) is 111,975 Da, characterizing this enzyme from reticulocytes as a homodimer of 224 kDa.
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PMID:The ubiquityl-calmodulin synthetase system from rabbit reticulocytes: isolation of the ubiquitin-binding first component, a ubiquitin-activating enzyme. 971 91


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