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We critically compared Marcusenius specimens from the mouth of the Cunene River on the Namibia/Angola border, a harsh desert environment on the Atlantic Ocean coast virtually devoid of aerial insects with aquatic larvae which are an important food item, with Marcusenius multisquamatus Kramer & Wink, 2013 from the escarpment region of that same river, in a relatively rich and productive subtropical savannah environment. River mouth specimens were differentiated in morphology and electric organ discharges, as determined by ANOVA/MANOVA comparisons, principal component and discriminant analyses on morphological and electrophysiological characters, and genetics, including sequences of the mitochondrial cytochrome b gene, indicating reproductive isolation. Specimens from the river mouth differed from M. multisquamatus, their closest relatives, by having a shorter snout, a smaller eye diameter, and smaller nares separation. River mouth specimens were also differentiated from other, increasingly less-close relatives, such as M. altisambesi Kramer et al., 2007 from the Okavango River, Botswana, and from M. krameri Maake et al., 2014 from the Limpopo System, South Africa. We therefore designate the new species Marcusenius desertus sp. nov. for the Cunene River mouth population. 相似文献
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Owen W. Nadeau Laura A. Lane Dong Xu Jessica Sage Timothy S. Priddy Antonio Artigues Maria T. Villar Qing Yang Carol V. Robinson Yang Zhang Gerald M. Carlson 《The Journal of biological chemistry》2012,287(44):36651-36661
Phosphorylase kinase (PhK) is a hexadecameric (αβγδ)4 complex that regulates glycogenolysis in skeletal muscle. Activity of the catalytic γ subunit is regulated by allosteric activators targeting the regulatory α, β, and δ subunits. Three-dimensional EM reconstructions of PhK show it to be two large (αβγδ)2 lobes joined with D2 symmetry through interconnecting bridges. The subunit composition of these bridges was unknown, although indirect evidence suggested the β subunits may be involved in their formation. We have used biochemical, biophysical, and computational approaches to not only address the quaternary structure of the β subunits within the PhK complex, i.e. whether they compose the bridges, but also their secondary and tertiary structures. The secondary structure of β was determined to be predominantly helical by comparing the CD spectrum of an αγδ subcomplex with that of the native (αβγδ)4 complex. An atomic model displaying tertiary structure for the entire β subunit was constructed using chemical cross-linking, MS, threading, and ab initio approaches. Nearly all this model is covered by two templates corresponding to glycosyl hydrolase 15 family members and the A subunit of protein phosphatase 2A. Regarding the quaternary structure of the β subunits, they were directly determined to compose the four interconnecting bridges in the (αβγδ)4 kinase core, because a β4 subcomplex was observed through both chemical cross-linking and top-down MS of PhK. The predicted model of the β subunit was docked within the bridges of a cryoelectron microscopic density envelope of PhK utilizing known surface features of the subunit. 相似文献
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Single molecule analyses of the conformational substates of calmodulin bound to the phosphorylase kinase complex
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Priddy TS Price ES Johnson CK Carlson GM 《Protein science : a publication of the Protein Society》2007,16(6):1017-1023
The four integral delta subunits of the phosphorylase kinase (PhK) complex are identical to calmodulin (CaM) and confer Ca(2+) sensitivity to the enzyme, but bind independently of Ca(2+). In addition to binding Ca(2+), an obligatory activator of PhK's phosphoryltransferase activity, the delta subunits transmit allosteric signals to PhK's remaining alpha, beta, and gamma subunits in activating the enzyme. Under mild conditions about 10% of the delta subunits can be exchanged for exogenous CaM. In this study, a CaM double-mutant derivatized with a fluorescent donor-acceptor pair (CaM-DA) was exchanged for delta to assess the conformational substates of PhKdelta by single molecule fluorescence resonance energy transfer (FRET) +/-Ca(2+). The exchanged subunits were determined to occupy distinct conformations, depending on the absence or presence of Ca(2+), as observed by alterations of the compact, mid-length, and extended populations of their FRET distance distributions. Specifically, the combined predominant mid-length and less common compact conformations of PhKdelta became less abundant in the presence of Ca(2+), with the delta subunits assuming more extended conformations. This behavior is in contrast to the compact forms commonly observed for many of CaM's Ca(2+)-dependent interactions with other proteins. In addition, the conformational distributions of the exchanged PhKdelta subunits were distinct from those of CaM-DA free in solution, +/-Ca(2+), as well as from exogenous CaM bound to the PhK complex as delta'. The distinction between delta and delta' is that the latter binds only in the presence of Ca(2+), but stoichiometrically and at a different location in the complex than delta. 相似文献
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Ovarian follicular fluid eicosanoid concentrations during the pre-ovulatory period in humans 总被引:2,自引:0,他引:2
A R Priddy S R Killick M Elstein J Morris M Sullivan L Patel M G Elder 《Prostaglandins》1989,38(2):197-202
Prostaglandins are involved in ovulation and in every mammal studied so far, ovulation has been inhibited by prostaglandin inhibition. Information regarding the role of leukotrienes and thromboxanes in ovulation is more limited. In order to study the production of eicosanoids in human pre-ovulatory follicular fluid, follicular aspiration was timed by means of serial ultrasound scans and human chorionic gonadotrophin (hCG) to be immediately pre-ovulatory. 11 women were studied and the eicosanoids measured by radioimmunoassay (RIA). The follicular fluid was found to contain leukotrienes (LT) B4, LTC4 (D4, E4), prostaglandin (PG) E2, PGF2 alpha 6 keto PGF1 alpha k and thromboxane (TX) B2. This is the first published report of leukotrienes in human follicular fluid in spontaneous cycles, and is one of the few reports showing prostaglandins and thromboxanes. The significance of demonstrating leukotrienes in human follicular fluid is discussed as is the correlation between individual eicosanoids in the human ovary. 相似文献
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We report here the structural determination of N-linked oligosaccharides
found on extracellular hemoglobins of the hydrothermal vent tube worm
Riftia pachyptila. Structures were elucidated by a combination of
electrospray ionization tandem mass spectrometry, matrix- assisted laser
desorption/ionization mass spectrometry, normal-phase high performance
liquid chromatography, and exoglycosidase digestion. The sugar chains were
found to consist mainly of high-mannose-type glycans with some structures
partially capped by one or two terminal glucose residues. The present study
represents the first report of the occurrence of glucose capping of
N-linked carbohydrates in a secreted glycoprotein of a metazoan.
Previously, glucose capping has only been described for a membrane-bound
surface glycoprotein from the unicellular parasite Leishmania mexicana
amazonensis.
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