A 6.2-kb full-length clone encoding a distinct protein-tyrosine phosphatase (PTP; EC 3.1.3.48), PTPD1, was isolated from a human skeletal muscle cDNA library. The cDNA encodes a protein of 1174 amino ...acids with N-terminal sequence homology to the ezrin-band 4.1-merlin-radixin protein family, which also includes the two PTPs H1 and MEG1. The PTP domain is positioned in the extreme C-terminal part of PTPD1, and there is an intervening sequence of about 580 residues without any apparent homology to known proteins separating the ezrin-like and the PTP domains. Thus, PTPD1 and the closely related, partially characterized, PTPD2 belong to the same family as PTPH1 and PTPMEG1, but because of distinct features constitute a different PTP subfamily. Northern blot analyses indicate that PTPD1 and PTPD2 are expressed in a variety of tissues. In transient coexpression experiments PTPD1 was found to be efficiently phosphorylated by and associated with the src kinase pp60src.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Major surgery is accompanied by extensive proteolysis of insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3). Proteolysis of IGFBP-3 is generally believed to increase IGF bioavailability due ...to a diminished affinity of the IGFBP-3 fragments for IGFs. We have investigated 18 patients undergoing elective ileo-anal J-pouch surgery. Patients were randomized to treatment with GH (12 IU/day; n = 9) or placebo (n = 9) from 2 days before to 7 days after operation. Free IGF-I and IGF-II were measured by ultrafiltration of serum, and IGFBP-3 proteolytic activity was determined by a 125Irecombinant human IGFBP-3 degradation assay. In the GH-treated group, total IGF-I increased preoperatively by 99%. Postoperatively, total IGF-I decreased by 48% (placebo) and 52% (GH). Immunoassayable IGFBP-3 decreased by 27% (placebo) and 26% (GH). In the placebo-treated group, free IGF-I was unchanged throughout the study. In the GH-treated group, free IGF-I increased by 277% preoperatively and remained elevated after operation. IGFBP-3 proteolytic activity increased by 63-73% after operation. The relative elevations of free IGF-I levels despite decreased total IGF-I levels could thus relate to augmented IGFBP-3 proteolysis.
Our aim in this paper is to refine the orbital and physical parameters of the HATS-2 planetary system and study transit timing variations and atmospheric composition thanks to transit observations ...that span more than ten years and that were collected using different instruments and pass-band filters. We also investigate the orbital alignment of the system by studying the anomalies in the transit light curves induced by starspots on the photosphere of the parent star. We analysed new transit events from both ground-based telescopes and NASA's TESS mission. Anomalies were detected in most of the light curves and modelled as starspots occulted by the planet during transit events. We fitted the clean and symmetric light curves with the JKTEBOP code and those affected by anomalies with the PRISM+GEMC codes to simultaneously model the photometric parameters of the transits and the position, size, and contrast of each starspot. We found consistency between the values we found for the physical and orbital parameters and those from the discovery paper and ATLAS9 stellar atmospherical models. We identified different sets of consecutive starspot-crossing events that temporally occurred in less than five days. Under the hypothesis that we are dealing with the same starspots, occulted twice by the planet during two consecutive transits, we estimated the rotational period of the parent star and, in turn the projected and the true orbital obliquity of the planet. We find that the system is well aligned. We identified the possible presence of transit timing variations in the system, which can be caused by tidal orbital decay, and we derived a low-resolution transmission spectrum.
HATS-18b is a transiting planet with a large mass and a short orbital period, and is one of the best candidates for the detection of orbital decay induced by tidal effects. We present extensive ...photometry of HATS-18 from which we measure 27 times of mid-transit. Two further transit times were measured from data from the Transiting Exoplanet Survey Satellite (TESS) and three more taken from the literature. The transit timings were fitted with linear and quadratic ephemerides and an upper limit on orbital decay was determined. This corresponds to a lower limit on the modified stellar tidal quality factor of \(Q_\star^{\,\prime} > 10^{5.11 \pm 0.04}\). This is at the cusp of constraining the presence of enhanced tidal dissipation due to internal gravity waves. We also refine the measured physical properties of the HATS-18 system, place upper limits on the masses of third bodies, and compare the relative performance of TESS and the 1.54-m Danish Telescope in measuring transit times for this system.
The aim of this study was to define the structural elements that determine the differences in substrate recognition capacity of two protein-tyrosine phosphatases (PTPs), PTP1B and PTPα, both ...suggested to be negative regulators of insulin signaling. Since the Ac-DADE(pY)L-NH2 peptide is well recognized by PTP1B, but less efficiently by PTPα, it was chosen as a tool for these analyses. Cα regiovariation analyses and primary sequence alignments indicate that residues 47, 48, 258, and 259 (PTP1B numbering) define a selectivity-determining region. By analyzing a set of DADE(pY)L analogs with a series of PTP mutants in which these four residues were exchanged between PTP1B and PTPα, either in combination or alone, we here demonstrate that the key selectivity-determining residue is 259. In PTPα, this residue is a glutamine causing steric hindrance and in PTP1B a glycine allowing broad substrate recognition. Significantly, replacing Gln259 with a glycine almost turns PTPα into a PTP1B-like enzyme. By using a novel set of PTP inhibitors and x-ray crystallography, we further provide evidence that Gln259 in PTPα plays a dual role leading to restricted substrate recognition (directly via steric hindrance) and reduced catalytic activity (indirectly via Gln262). Both effects may indicate that PTPα regulates highly selective signal transduction processes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Six Outbursts of Comet 46P/Wirtanen Kelley, Michael S P; Farnham, Tony L; Jian-Yang, Li ...
Discovery Research Portal (University of Dundee),
05/2021
Paper, Journal Article
Open access
Cometary activity is a manifestation of sublimation-driven processes at the surface of nuclei. However, cometary outbursts may arise from other processes that are not necessarily driven by volatiles. ...In order to fully understand nuclear surfaces and their evolution, we must identify the causes of cometary outbursts. In that context, we present a study of mini-outbursts of comet 46P/Wirtanen. Six events are found in our long-term lightcurve of the comet around its perihelion passage in 2018. The apparent strengths range from \(-0.2\) to \(-1.6\) mag in a 5" radius aperture, and correspond to dust masses between \(\sim10^4\) to \(10^6\) kg, but with large uncertainties due to the unknown grain size distributions. However, the nominal mass estimates are the same order of magnitude as the mini-outbursts at comet 9P/Tempel 1 and 67P/Churyumov-Gerasimenko, events which were notably lacking at comet 103P/Hartley 2. We compare the frequency of outbursts at the four comets, and suggest that the surface of 46P has large-scale (\(\sim\)10-100 m) roughness that is intermediate to that of 67P and 103P, if not similar to the latter. The strength of the outbursts appear to be correlated with time since the last event, but a physical interpretation with respect to solar insolation is lacking. We also examine Hubble Space Telescope images taken about 2 days following a near-perihelion outburst. No evidence for macroscopic ejecta was found in the image, with a limiting radius of about 2-m.
To examine the role of the N-terminal part of the insulin-like growth factor I (IGF-I) receptor and insulin receptor in determining ligand specificity, we prepared an expression vector encoding a ...hybrid receptor where exon 1 (encoding the signal peptide and seven amino acids of the alpha-subunit), exon 2, and exon 3 of the insulin receptor were replaced with the corresponding IGF-I receptor cDNA (938 nucleotides). To allow direct quantitative comparison of the binding capabilities of this hybrid receptor with those of the human IGF-I receptor and the insulin receptor, all three receptors were expressed in baby hamster kidney (BHK) cells as soluble molecules and partially purified before characterization. The hybrid IGF-I/insulin receptor bound IGF-I with an affinity comparable to that of the wild-type IGF-I receptor. In contrast, the hybrid receptor no longer displayed high-affinity binding of insulin. These results directly demonstrate that it is possible to change the specificity of the insulin receptor to that of the IGF-I receptor and, furthermore, that the binding specificity for IGF-I is encoded within the nucleotide sequence from 135 to 938 of the IGF-I receptor cDNA. Since the hybrid receptor only bound insulin with low affinity, the insulin binding region is likely to be located within exons 2 and 3 of the insulin receptor.
Human β
2-glycoprotein (β
2gpI) cDNA was isolated from a liver cDNA library and sequenced. The cDNA encoded a 19-residue hydrophobic signal peptide followed by the mature β
2gpI of 326 amino acid ...residues. In liver and in the hepatoma cell line HepG2 there are two mRNA species of about 1.4 and 4.3 kb, respectively, hybridizing specifically with the β
2gpI cDNA. Upon isoelectric focusing, recombinant β
2gpI obtained from expression of β
2gpI cDNA in baby hamster kidney cells showed the same pattern of bands as β
2gpI isolated from plasma, and at least 5 polypeptides were visible
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BFBNIB, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Context. Brown dwarfs are poorly understood transition objects between stars and planets, with several competing mechanisms having been proposed for their formation. Mass measurements are generally ...difficult for isolated objects but also for brown dwarfs orbiting low-mass stars, which are often too faint for spectroscopic follow-up. Aims. Microlensing provides an alternative tool for the discovery and investigation of such faint systems. Here we present the analysis of the microlensing event OGLE-2019-BLG-0033/MOA-2019-BLG-035, which is due to a binary system composed of a brown dwarf orbiting a red dwarf. Methods. Thanks to extensive ground observations and the availability of space observations from Spitzer, it has been possible to obtain accurate estimates of all microlensing parameters, including parallax, source radius and orbital motion of the binary lens. Results. After accurate modeling, we find that the lens is composed of a red dwarf with mass \(M_1 = 0.149 \pm 0.010M_\odot\) and a brown dwarf with mass \(M_2 = 0.0463 \pm 0.0031M_\odot\), at a projected separation of \(a_\perp = 0.585\) au. The system has a peculiar velocity that is typical of old metal-poor populations in the thick disk. Percent precision in the mass measurement of brown dwarfs has been achieved only in a few microlensing events up to now, but will likely become common with the Roman space telescope.
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