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101.
Homothorax switches function of Drosophila photoreceptors from color to polarized light sensors 总被引:1,自引:0,他引:1
Different classes of photoreceptors (PRs) allow animals to perceive various types of visual information. In the Drosophila eye, the outer PRs of each ommatidium are involved in motion detection while the inner PRs mediate color vision. In addition, flies use a specialized class of inner PRs in the "dorsal rim area" of the eye (DRA) to detect the e-vector of polarized light, allowing them to exploit skylight polarization for orientation. We show that homothorax is both necessary and sufficient for inner PRs to adopt the polarization-sensitive DRA fate instead of the color-sensitive default state. Homothorax increases rhabdomere size and uncouples R7-R8 communication to allow both cells to express the same opsin rather than different ones as required for color vision. Homothorax expression is induced by the iroquois complex and the wingless (wg) pathway. However, crucial wg pathway components are not required, suggesting that additional signals are involved. 相似文献
102.
Charton I Suzenet F Boutin JA Audinot V Delagrange P Bennejean C Renard P Guillaumet G 《Journal of enzyme inhibition and medicinal chemistry》2003,18(2):187-193
The synthesis of benzoxathiins bearing a retroamide function is described from 8-hydroxythiochroman, the key step involving the synthesis of the benzoxathiin ring through a sulfonium salt. These new melatonin analogues were evaluated on human receptors MT1 and MT2 and have a similar affinity to that of melatonin itself. 相似文献
103.
Macromolecular assemblies containing multiple protein subunits and having masses in the megadalton (MDa) range are involved
in most of the functions of a living cell. Because of variation in the number and masses of subunits, macromolecular assemblies
do not have a unique mass, but rather a mass distribution. The giant extracelular erythrocruorins (Ers), ∼ 3.5 MDa, comprized
of at least 180 polypeptide chains, are one of the best characterized assemblies. Three-dimensional reconstructions from cryoelectron
microscopic images show them to be hexagonal bilayer complexes of 12 subassemblies, each comprised of 12 globin chains, anchored
to a subassembly of 36 nonglobin linker chains. We have calculated the most probable mass distributions forLumbricus andRiftia assemblies and their globin and linker subassemblies, based on theLumbricus Er stoichiometry and using accurate subunit masses obtained by electrospray ionization mass spectrometry. The expected masses
ofLumbricus andRiftia Ers are 3.517 MDa and 3.284 MDa, respectively, with a possible variation of ∼ 9% due to the breadth of the mass distributions.
TheLumbricus Er mass is in astonishingly good agreement with the mean of 23 known masses, 3.524 ± 0.481 MDa. 相似文献
104.
105.
Improved gelatinase a selectivity by novel zinc binding groups containing galardin derivatives 总被引:1,自引:0,他引:1
Augé F Hornebeck W Decarme M Laronze JY 《Bioorganic & medicinal chemistry letters》2003,13(10):1783-1786
The synthesis of several analogues of galardin, a MMP inhibitor, are presented with their in vitro inhibitory activity against MMP-1 and MMP-2. These compounds contain a distinct Zinc Binding Group (ZBG). Those having a 2-acylated-heterocycle as well as a 2-arylamide function do not exhibit a good inhibition/selectivity against the enzymes tested. On the contrary, those that are based on a hydrazide scaffold present potent selectivity for MMP-2 versus MMP-1. 相似文献
106.
Regulation of etioplast pigment-protein complexes, inner membrane architecture, and protochlorophyllide a chemical heterogeneity by light-dependent NADPH:protochlorophyllide oxidoreductases A and B
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Franck F Sperling U Frick G Pochert B van Cleve B Apel K Armstrong GA 《Plant physiology》2000,124(4):1678-1696
The etioplast of dark-grown angiosperms is characterized by the prolamellar body (PLB) inner membrane, the absence of chlorophyll, and the accumulation of divinyl and monovinyl derivatives of protochlorophyll(ide) a [Pchl(ide) a]. Either of two structurally related, but differentially expressed light-dependent NADPH:Pchlide oxidoreductases (PORs), PORA and PORB, can assemble the PLB and form dark-stable ternary complexes containing enzymatically photoactive Pchlide-F655. Here we have examined in detail whether these polypeptides play redundant roles in etioplast differentiation by manipulating the total POR content and the PORA-to-PORB ratio of etiolated Arabidopsis seedlings using antisense and overexpression approaches. POR content correlates closely with PLB formation, the amounts, spectroscopic properties, and photoreduction kinetics of photoactive Pchlide, the ratio of photoactive Pchlide-F655 to non-photoactive Pchl(ide)-F632, and the ratio of divinyl- to monovinyl-Pchl(ide). This last result defines POR as the first endogenous protein factor demonstrated to influence the chemical heterogeneity of Pchl(ide) in angiosperms. It is intriguing that excitation energy transfer between different spectroscopic forms of Pchl(ide) in etiolated cotyledons remains largely independent of POR content. We therefore propose that the PLB contains a minimal structural unit with defined pigment stoichiometries, within which a small amount of non-photoactive Pchl(ide) transfers excitation energy to a large excess of photoactive Pchlide-F655. In addition, our data suggests that POR may bind not only stoichiometric amounts of photoactive Pchlide, but also substoichiometric amounts of non-photoactive Pchl(ide). We conclude that the typical characteristics of etioplasts are closely related to total POR content, but not obviously to the specific presence of PORA or PORB. 相似文献
107.
Pierre Franck Lionel Garnery Michel Solignac Jean-Marie Cornuet 《Evolution; international journal of organic evolution》1998,52(4):1119-1134
Apis mellifera is composed of three evolutionary branches including mainly African (branch A), western and northern European (branch M), and southeastern European (branch C) populations. The existence of morphological clines extending from the equator to the Polar Circle through Morocco and Spain raised the hypothesis that the branch M originated in Africa. Mitochondrial DNA analysis revealed that branches A and M were characterized by highly diverged lineages implying very remote links between both branches. It also revealed that mtDNA haplotypes from lineages A coexisted with haplotypes M in the Iberian Peninsula and formed a south-north frequency cline, suggesting that this area could be a secondary contact zone between the two branches. By analyzing 11 populations sampled along a France-Spain/Portugal-Morocco-Guinea transect at 8 microsatellite loci and the DraI RFLP of the COI-COII mtDNA marker, we show that Iberian populations do not present any trace of “africanization” and are very similar to French populations when considering microsatellite markers. Therefore, the Iberian Peninsula is not a transition area. The higher haplotype A variability observed in Spanish and Portuguese samples compared to that found in Africa is explained by a higher mutation rate and multiple and recent introductions. Selection appears to be the best explanation to the morphological and allozymic clines and to the diffusion and maintenance of African haplotypes in Spain and Portugal. 相似文献
108.
Cross-Reactions between the Cytotoxic T-Lymphocyte Responses of Human Immunodeficiency Virus-Infected African and European Patients 总被引:13,自引:5,他引:8
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Deniz Durali Jacques Morvan Franck Letourneur Doris Schmitt Nelly Guegan Marc Dalod Sentob Saragosti Didier Sicard Jean-Paul Levy Elisabeth Gomard 《Journal of virology》1998,72(5):3547-3553
The great variability of protein sequences from human immunodeficiency virus (HIV) type 1 (HIV-1) isolates represents a major obstacle to the development of an effective vaccine against this virus. The surface protein (Env), which is the predominant target of neutralizing antibodies, is particularly variable. Here we examine the impact of variability among different HIV-1 subtypes (clades) on cytotoxic T-lymphocyte (CTL) activities, the other major component of the antiviral immune response. CTLs are produced not only against Env but also against other structural proteins, as well as some regulatory proteins. The genetic subtypes of HIV-1 were determined for Env and Gag from several patients infected either in France or in Africa. The cross-reactivities of the CTLs were tested with target cells expressing selected proteins from HIV-1 isolates of clade A or B or from HIV type 2 isolates. All African patients were infected with viruses belonging to clade A for Env and for Gag, except for one patient who was infected with a clade A Env-clade G Gag recombinant virus. All patients infected in France were infected with clade B viruses. The CTL responses obtained from all the African and all the French individuals tested showed frequent cross-reactions with proteins of the heterologous clade. Epitopes conserved between the viruses of clades A and B appeared especially frequent in Gag p24, Gag p18, integrase, and the central region of Nef. Cross-reactivity also existed among Gag epitopes of clades A, B, and G, as shown by the results for the patient infected with the clade A Env-clade G Gag recombinant virus. These results show that CTLs raised against viral antigens from different clades are able to cross-react, emphasizing the possibility of obtaining cross-immunizations for this part of the immune response in vaccinated individuals. 相似文献
109.
110.
N. André Sasaki Maria Concepcion Garcia-Alvarez Qian Wang Ludmila Ermolenko Gisèle Franck Naïma Nhiri Marie-Thérèse Martin Nicolas Audic Pierre Potier 《Bioorganic & medicinal chemistry》2009,17(6):2310-2320
2,3-Diaminopropionic acid (Dap) and N-terminal Dap peptides have been found to inhibit in vitro protein-modifications by methylglyoxal (MG), one of the highly reactive α-dicarbonyl compounds. MG scavenging potency of the newly synthesized N-terminal Dap peptides is demonstrated by RP-HPLC, SDS–PAGE and non-denaturing PAGE analysis, assays for enzymatic activity and cell viability study and was compared with that of known AGE inhibitors, such as aminoguanidine, pyridoxamine, metformin and carnosine. Two addition products of MG and l-Dap-l-Leu are separated by HPLC and their chemical structures are characterized by 1H and 13C NMR spectroscopy to indicate that both of them are pyrazines derived from 2 molecules of MG and 1 molecule of l-Dap-l-Leu. Mutagenic activities of l-Dap-l-Leu and l-Dap-l-Val and their metabolites according to the Ames assay are found to be negative. 相似文献