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1.
Jos C. García‐Borrn Berta L. Snchez‐Laorden Celia Jimnez‐Cervantes 《Pigment cell & melanoma research》2005,18(6):393-410
The melanogenic actions of the melanocortins are mediated by the melanocortin‐1 receptor (MC1R). MC1R is a member of the G‐protein‐coupled receptors (GPCR) superfamily expressed in cutaneous and hair follicle melanocytes. Activation of MC1R by adrenocorticotrophin or α‐melanocyte stimulating hormone is positively coupled to the cAMP signaling pathway and leads to a stimulation of melanogenesis and a switch from the synthesis of pheomelanins to the production of eumelanic pigments. The functional behavior of the MC1R agrees with emerging concepts in GPCR signaling including dimerization, coupling to more than one signaling pathway and a high agonist‐independent constitutive activity accounting for inverse agonism phenomena. In addition, MC1R displays unique properties such as an unusually high number of natural variants often associated with clearly visible phenotypes and the occurrence of endogenous peptide antagonists. Therefore MC1R is an ideal model to study GPCR function. Here we review our current knowledge of MC1R structure and function, with emphasis on information gathered from the analysis of natural variants. We also discuss recent data on the regulation of MC1R function by paracrine and endocrine factors and by external stimuli such as ultraviolet light. 相似文献
2.
Michael Brenowitz Celia Bonaventura Joseph Bonaventura Elisabetta Gianazza 《Archives of biochemistry and biophysics》1981,210(2):748-761
The hemocyanin of Limulus polyphemus is a 48-subunit aggregate. This 3.3 × 106-dalton oligomer is composed of structurally and functionally heterogeneous subunits. Using polyacrylamide electrophoresis J. Markl, A. Markl, W. Schartau, and B. Linzen (J. Comp. Physiol. Ser. B130,283–292, 1979) observed 12 bands; while using immunoelectrophoresis, M. Hoylaerts, G. Preaux, R. Witters, and R. Lontie (Arch. Int. Physiol. Biochem.87, 417–418, 1979) and J. Lamy, J. Lamy, J. Weill, J. Bonaventura, C. Bonaventura, and M. Brenowitz. (Arch. Biochem. Biophys.196, 324–339, 1979) observed 8 subunits. To proceed with an analysis of subunit roles in assembly it is first necessary to determine the number of distinct subunits. Refinement of the chromatographic separation procedures has led to the isolation of 8 immunologically distinct subunits as well as additional charge isomers which cannot be distinguished immunologically. Alkaline electrophoresis revealed 15 bands and isoelectric focusing up to 17. On the basis of extensive control experiments, including composit acrylamide-agarose immunoelectrophoresis and checks for conformational isomers, aggregation, proteolysis, and other types of degradation, we conclude that the electrophoretic heterogeneity of immunologically identical subunits is not artifactual. We have extended the nomenclature used by Lamy et al. (1979) to include the electrophoretic heterogeneity by using primes (′) to denote electrophoretically distinguishable subunits which are immunologically identical. A number of patterns have become apparent by correlating the results obtained by the different techniques. For example, immunologically pure subunit II, which shows 3 bands on alkaline electrophoresis, is in fact a mixture of electrophoretically distinct subunits II, II′, II″. Except for subunits II, II′, and II″ immunoelectrophoretically identical subunits are typically homogeneous on sodium dodecyl sulfate-gels. However, slight differences in the apparent molecular weight are observed on high-resolution gels between immunologically unrelated subunits. The immunological identity and electrophoretic differences suggest that the charge isomers which are immunologically identical have similar antigenic surfaces. If a charge substitution is not in a critical location, we would expect the electrophoretically distinct but immunologically identical subunits to have identical assembly roles. Comparison of the results for Limulus hemocyanin with the hemocyanin of related species Eurypelma californicum and Androctanus australis, which have 7 and 8 immunologically distinct subunits, respectively, suggests that the calcium-mediated aggregation from 24 to 48 subunits of Limulus does not require more extensive subunit complexity. 相似文献
3.
Celia Gluzman de Pascar 《Hydrobiologia》1987,144(2):125-130
The Oligochaeta of some streams flowing into the Rio de La Plata, Buenos Aires, Argentina, were investigated. Twenty nine
taxa (twenty four naidids, five tubificids) were identified. Most species are cosmopolitan, but Dero evelinae, Pristina leidyi, Slavina isochaeta and Bothrioneurum sp. are neotropical. Bratislavia unidentata, Haemonais waldvogeli and Nais pardalis are reported for the first time in Argentina. Variants occurr in the shape of the distal end of the penial sheaths of Limnodrilus hoffmeisteri. The dominant Naidid genera are Dero and Pristina. In the polluted El Gato stream only L. hoffmeisteri and L. claparedeianus were found. 相似文献
4.
J. Allan Downie Gerd Hombrecher Qing-Sheng Ma Celia D. Knight Brian Wells Andrew W. B. Johnston 《Molecular & general genetics : MGG》1983,190(3):359-365
Summary Three nodulation-deficient (nod) mutants of Rhizobium leguminosarum were isolated following insertion of the transposon Tn5 into pRL1JI, the R. leguminosarum plasmid known to carry the nodulation genes. DNA adjacent to the nod: Tn5 alleles was subcloned and used to probe a cosmid clone bank containing DNA from a Rhizobium strain carrying pRL1JI. Two cosmid clones which showed homology with the probe contained about 10 kb of DNA in common. The R. leguminosarum host-range determinants were found to be present within this 10 kb common region since either of the cosmid clones could enable a cured R. phaseoli strain to nodulate peas instead of Phaseolus beans, its normal host. Electron microscopy of nodules induced by Rhizobium strains cured of their normal symbiotic plasmid but containing either of the two cosmid clones showed bacteroid-forms surrounded by a peri-bacteroid membrane, indicating that normal infection had occurred. Thus it is clear that this 10 kb region of nodDNA carries the genes that determine host range and that relatively few bacterial genes may be involved in nodule and bacteroid development. 相似文献
5.
Arhur G. Steinberg Celia P. Milstein Carla L. McLaughlin Alan Solomon 《Immunogenetics》1974,1(1):108-117
A Bence Jones protein with phenotype Inv (1, –2) was isolated from the urine of a patient with multiple myeloma. Inv typing of the patient's relatives established the presence of anInv
1 allele in the kindred, and that the patient's genotype wasInv
1/Inv
3. Hence, the absence of Inv (2) in the Bence Jones protein was shown to be genetic and not an artifact caused by the disease. The tryptic peptide-containing residues 191 through 194 were isolated and shown to be composed of Leu, Tyr, Ala, Cys, with Leu at the amino end. Hence, the residue at 191 is the same as that present in Inv (1, 2) Bence Jones proteins. More detailed study of the tryptic peptides established that residue 153 is Val rather than Ala as in all other K chains thus far studied. The primary sequence: Ala153, Leu191 determines Inv (1, 2); Ala153, Val191 determines Inv (3); and Val153, Leu191 determines Inv (1). The Val153, Val191 sequence has not been observed. It may correspond to Inv (–). These data are strikingly similar to the data for the Kern and Oz isotypes (changes at 154 and 191, respectively) in the chain. As in the case of theK chain, only three of the four possible combinations have been observed. The implications of this parallelism and of crystallographic findings on chains, reported by others, are discussed. 相似文献
6.
An application of diagonal electrophoresis to the selective purification of serine phosphate peptides. Serine phosphate peptides from ovalbumin 总被引:5,自引:3,他引:2 下载免费PDF全文
Celia P. Milstein 《The Biochemical journal》1968,110(1):127-134
A diagonal-electrophoresis method for the selective purification of serine phosphate peptides was applied to tryptic, chymotryptic and peptic digests of oxidized ovalbumin. This method is based on the release of the phosphate group bound to serine by treatment with alkaline phosphatase on paper. The identified serine phosphate peptides were purified by paper electrophoresis at pH6.5 and 2.0, dephosphorylation with bacterial alkaline phosphatase, and paper electrophoresis at pH2.0 again, in that order. The presence of two groups of serine phosphate peptides was apparent from the amino acid composition. One group contained no lysine, cysteic acid, proline, leucine or isoleucine (sequence 1) and the other had all those amino acids (sequence 2). Further degradation with subtilisin of those peptides and ;dansyl'-Edman sequence analysis established their partial sequences. The proposed sequences are as follows (with ;SerP' representing serine phosphate): sequence 1, -Ala-Gly-Arg-Glu-Val-Val-Gly-SerP-Ala-Glu-Ala-Gly-Asp-Val-Ala-Ala-Ser-(Val,Glx(2),Ser,Phe)-Arg-; sequence 2, -Asp-Lys-Leu-Pro-Gly-Phe-Gly-Asp-SerP-Ile-Glx-Ala-Glx-CySO(3)H-Gly-(Thr,Ser,Val)-(Asp,His,Val)-. The partial sequence of one of the phosphopeptides, Asp-(Glu,Ile,SerP), reported by Flavin (1954) was used to establish the proposed sequence 2. 相似文献
7.
Niraj Shrestha Pallavi Chaturvedi Xiaoyun Zhu Michael J. Dee Varghese George Christopher Janney Jack O. Egan Bai Liu Mark Foster Lynne Marsala Pamela Wong Celia C. Cubitt Jennifer A. Foltz Jennifer Tran Timothy Schappe Karin Hsiao Gilles M. Leclerc Lijing You Christian Echeverri Catherine Spanoudis Ana Carvalho Leah Kanakaraj Crystal Gilkes Nicole Encalada Lin Kong Meng Wang Byron Fang Zheng Wang Jin-an Jiao Gabriela J. Muniz Emily K. Jeng Nicole Valdivieso Liying Li Richard Deth Melissa M. Berrien-Elliott Todd A. Fehniger Peter R. Rhode Hing C. Wong 《Aging cell》2023,22(5):e13806
8.
Celia Roberts 《American anthropologist》2003,105(3):670-671
Contraception across Cultures: Technologies, Choices, Constraints. Andrew Russell. Elisa J. Sobo. and Mary S. Thompson. Oxford: Berg Publishers, 2000. 224 pp. 相似文献
9.
Herv Celia James D. Jontes Michael Whittaker Ronald A. Milligan 《Journal of structural biology》1996,117(3):236-241
Brush border myosin-I (BBMI) is a single-headed unconventional myosin found in the microvilli of intestinal epithelial cells, where it links the core bundle of actin filaments to the plasma membrane. An association of BBMI with anionic phospholipids has been shown to be mediated by a carboxy-terminal domain which is rich in basic amino acids. We have exploited this natural affinity of BBMI for negatively charged lipids to form two-dimensional (2D) crystals of this protein which are suitable for structural analysis by electron crystallographic techniques. The 2D crystals which we have obtained belong to one of two space groups, p22121or p2. We present here projection maps calculated from images of negatively stained crystals for each of these crystal types to a resolution of 20 Å and show that the asymmetric unit is the same in both crystal types. 相似文献
10.
David E. Holm Gerald Godette Celia Bonaventura Joseph Bonaventura M. David Boatright Linda L. Pearce Jim Peterson 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》1996,114(4):345-352
Contrary to previous reports, the functional and spectral properties of “monomeric” shark cytochrome c oxidases are not entirely similar to those of the “dimeric” beef enzyme. Most significantly, unlike the behavior of beef oxidase, the fully oxidized shark enzyme is not reducible by carbon monoxide. Also, preparations of the shark enzyme, isolated at pH 7.8-8.0, lead to more than 60% of the sample always being obtained in a resting form, whereas similarly prepared beef oxidase is very often obtained, both by ourselves and others, exclusively in the pulsed form. Although the electronic absorption, magnetic circular dichroism and electron paramagnetic resonance (EPR) spectra of cytochrome c oxidase obtained from several shark species are similar to those of the beef enzyme, there are some significant differences. In particular, the Soret maximum is at 422 nm in the case of the fully oxidized resting shark oxidases at physiological pH and not 418 nm as commonly found for the beef enzyme. Moreover, the resting shark oxidases do not necessarily exhibit a “g = 12” signal in their EPR spectra. The turnover numbers of recent preparations of the shark enzyme are higher than previously reported and, interestingly, do not differ within experimental uncertainty from those documented for several beef isoenzymes assayed under comparable conditions. 相似文献