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91.
Two birds with one stone: genes that encode products targeted to two or more compartments 总被引:16,自引:0,他引:16
Eukaryotic cells are divided into multiple membrane-bound compartments, all of which contain proteins. A large subset of these proteins perform functions that are required in more than one compartment. Although in most cases proteins carrying out the same function in different compartments are encoded by different genes, this is not always true. Numerous examples have now been found where a single gene encodes proteins (or RNAs) found in two (or more) cell organelles or membrane systems. Some particularly clear examples come from protein synthesis itself: plant cells contain three protein-synthesizing compartments, the cytosol, the mitochondrial matrix and the plastid stroma. All three compartments thus require tRNAs and aminoacyl-tRNA synthetases. Some mitochondrial tRNAs and their aminoacyl-tRNA synthetases are identical to their cytosolic counterparts and they are encoded by the same genes. Similarly, some mitochondrial and plastid aminoacyl-tRNA synthetases are encoded by the same nuclear genes. The various ways in which differentially targeted products can be generated from single genes is discussed. 相似文献
92.
Guo LW Muradov H Hajipour AR Sievert MK Artemyev NO Ruoho AE 《The Journal of biological chemistry》2006,281(22):15412-15422
The unique feature of rod photoreceptor cGMP phosphodiesterase (PDE6) is the presence of inhibitory subunits (Pgamma), which interact with the catalytic heterodimer (Palphabeta) to regulate its activity. This uniqueness results in an extremely high sensitivity and sophisticated modulations of rod visual signaling where the Pgamma/Palphabeta interactions play a critical role. The quaternary organization of the alphabetagammagamma heterotetramer is poorly understood and contradictory patterns of interaction have been previously suggested. Here we provide evidence that supports a specific interaction, by systematically and differentially analyzing the Pgamma-binding regions on Palpha and Pbeta through photolabel transfer from various Pgamma positions throughout the entire molecule. The Pgamma N-terminal Val16-Phe30 region was found to interact with the Palphabeta GAFa domain, whereas its C terminus (Phe73-Ile87) interacted with the Palphabeta catalytic domain. The interactions of Pgamma with these two domains were bridged by its central Ser40-Phe50 region through interactions with GAFb and the linker between GAFb and the catalytic domain, indicating a linear and extended interaction between Pgamma and Palphabeta. Furthermore, a photocross-linked product alphabetagamma(gamma) was specifically generated by the double derivatized Pgamma, in which one photoprobe was located in the polycationic region and the other in the C terminus. Taken together the evidence supports the conclusion that each Pgamma molecule binds Palphabeta in an extended linear interaction and may even interact with both Palpha and Pbeta simultaneously. 相似文献
93.
Sujal M. Parikh Ekwaro A. Obuku Sarah A. Walker Aggrey S. Semeere Brandon J. Auerbach James G. Hakim Harriet Mayanja-Kizza Peter N. Mugyenyi Robert A. Salata Cissy M. Kityo 《PloS one》2013,8(10)
Objective
Clinical and immunological data about HIV in older adults from low and middle income countries is scarce. We aimed to describe differences between younger and older adults with HIV starting antiretroviral therapy in two low–income African countries.Methods
Setting: HIV clinics in Uganda and Zimbabwe. Design: Secondary exploratory cross-sectional analysis of the DART randomized controlled trial. Outcome Measures: Clinical and laboratory characteristics were compared between adults aged 18-49 years (younger) and ≥ 50 years (older), using two exploratory multivariable logistic regression models, one with HIV viral load (measured in a subset pre-ART) and one without.Results
A total of 3316 eligible participants enrolled in DART were available for analysis; 219 (7%) were ≥ 50 years and 1160 (35%) were male. Across the two adjusted regression models, older adults had significantly higher systolic blood pressure, lower creatinine clearance and were consistently less likely to be females compared to younger adults with HIV. Paradoxically, the models separately suggested that older adults had statistically significant (but not clinically important) higher CD4+ cell counts and higher plasma HIV–1 viral copies at initiation. Crude associations between older age and higher baseline hemoglobin, body mass index, diastolic blood pressure and lower WHO clinical stage were not sustained in the adjusted analysis.Conclusions
Our study found clinical and immunological differences between younger and older adults, in a cohort of Africans starting antiretroviral therapy. Further investigations should explore how these differences could be used to ensure equity in service delivery and affect outcomes of antiretroviral therapy. 相似文献94.
El Abed K Rebai H Bloomer RJ Trabelsi K Masmoudi L Zbidi A Sahnoun Z Hakim A Tabka Z 《Journal of strength and conditioning research / National Strength & Conditioning Association》2011,25(9):2400-2409
It is well recognized that acute strenuous exercise is accompanied by an increase in free-radical production and subsequent oxidative stress, in addition to changes in blood antioxidant status. Chronic exercise provides protection against exercise-induced oxidative stress by upregulating endogenous antioxidant defense systems. Little is known regarding the protective effect afforded by judo exercise. Therefore, we determined antioxidant and oxidative stress biomarkers at rest and in response to acute exercise in 10 competitive judokas and 10 sedentary subjects after mixed exercise (anaerobic followed by aerobic). The subjects performed a Wingate test, followed by 30 minutes of aerobic exercise performed at 60% of maximal aerobic power. Blood samples were taken, by an intravenous catheter, at rest (R), immediately after the physical exercise (P0), and at 5 (P5), 10 (P10), and 20 (P20) minutes postexercise. The measured parameters included the activity of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and glutathione reductase, in addition to α-tocopherol, and total antioxidant status. Malondialdehyde was measured as a representation of lipid peroxidation. At rest, the judokas had higher values for all antioxidant and oxidative stress markers as compared to the sedentary subjects (p < 0.05). Plasma concentrations of all parameters except for α-tocopherol increased significantly above resting values for both the judokas and sedentary subjects (p < 0.05) and remained elevated at 20 minutes postexercise. A significant postexercise decrease was observed for α-tocopherol (p < 0.05) at P20 for judokas and at P5 for sedentary subjects. These data indicate that competitive judo athletes have higher endogenous antioxidant protection compared to sedentary subjects. However, both groups of subjects experience an increase in exercise-induced oxidative stress that is not different. 相似文献
95.
This study demonstrates that oxidative stress induced in rat thymocytes by the hydrophilic 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH), the lipophilic cumene hydroperoxide (CumOOH) and the freely diffusible H2O2 is associated with an activation of facilitative glucose transport rate, mediated by GLUT1, the major transporter in this cell type. We compared the effects of the three tested radical sources on the kinetic transport parameters, showing that the transport rate enhancement in the treated cells can be ascribed to an increase in the Vmax value, apart from the site of generation of the oxidative stress. The enhancement of glucose transport by the three oxidants in thymocytes was significantly attenuated both by protein tyrosine kinase inhibitors as genistein and tyrphostin A23 and by U73122, a phospholipase C inhibitor. Genistein and U73122 reversed also the cited increase of Vmax values. It is concluded that the stimulation of glucose transport in response to different oxidants is mediated, at least in part, through reactive oxygen species (ROS)-induced stimulation of protein tyrosine kinase and phospholipase C pathways. 相似文献
96.
L. Ammar-Keskes R. Gdoura F. Bouzid F. Ben Salah D. Sellami H. Hakim A. Hammami T. Rebaï S. Rekik J. Orfila 《Andrologie》1998,8(1):25-35
Chlamydia trachomatis (CT) genital infection is one of the most frequent causes of infertility. Its repercution on semen parameters and male infertility is controversial. The objective of this study was to evaluate the impact of CT genital infection on semen parameters in male partners of infertile couples. Ninety-seven infertile couples were studied. Semen, urethral and cervical samples were tested for CT by means of direct fluorescence antibodies assay (DFA), cell culture, polymerase chain reaction (PCR) and FLISA. Sera from both parteners were tested for immunoglobulin M, A and G antibodies to Chlamydia by means of the microimmunofluorescence MIF). For all mens, standard semen parameters were analysed according to the guidlines of the word health organisation. CT infection was identified in 34% of the male partners. In 76% of cases, the infection was asymptomatic. 60,6% of infected patients’s wives were also infected by CT. There was no significant difference between the mean values of concentration, motility and morphology of spermatozoa in both groups of male patients, infected by CT (CT+ group) and lacked infection (CT-group). The mean values of motility, vitality, concentration and normal forms of spermatozoa, in both CT+ and CT- groups were respectively: 39,6%±17,5% vs 40,4% ± 14,9%, 61,9% ±18,1% vs 62,4% ± 18,5%, 80,7×106±67,5×106 vs 67,1×106 ±65,2×106 and 34,7% ± 16,7% vs 33% ± 0,1%. Oligospermia was significantly more frequent in CT+ group (54,9%) than in CT-group (26,9%). High levels of coiled flagella (≥20) were more frequently observed in CT+ group (18,5%) than in CT-group (7,4%), but the difference was not significant. We found in this study a high prevalence of genital chlamydial infection into infertile couples. This infection has no repercution on sperm quality, suggesting that there is no effect of CT upon the spermatozoa. But, we can not exclude any impact on fertilisation ability and/or ultrastructure of these gametes. The finding that oligospermia was more frequent in CT+group, leds us to suggest thas chlamydial infection has a repercution on the gametogenesis or on genital ducts permeability. Another hypothesis would be that oligospermia, reflect of spermatogenesis disorder would be associated with reduction of local immunity. Other studies with wide exploration of spermatic functions and of different parts of genital tract are needed to specify the real impact of genital chlamydial infection upon men reproduction function. 相似文献
97.
98.
C Combadière J Hakim J P Giroud A Périanin 《Biochemical and biophysical research communications》1990,168(1):65-70
Staurosporine (STAR), a potent protein kinase C (PKC) antagonist, was found to modulate the chemoattractant-induced respiratory burst of human polymorphonuclear leukocytes (PMNs) according to drug concentration. Low STAR concentrations from 10 to 200 nM potentiated the N-formyl-methionyl-leucyl-phenylalanine (fMLP) and platelet activating factor (Paf)-induced respiratory burst, affecting both the initial rate and the total amount of superoxide anion generated. The maximal increase occurred in the presence of 100 nM STAR and optimal fMLP concentration and reached 60-100% of control values. Above 250 nM, STAR inhibited the respiratory burst with an IC50 of 360 and 320 nM for fMLP and Paf, respectively. The respiratory burst induced by PKC activators such as phorbol myristate acetate or phorbol 12, 13 dibutyrate was inhibited effectively by STAR, with a low IC50 (25 nM) for both stimuli. Thus, the use of low STAR concentrations points to two possible roles of PKC in the regulation of NADPH oxidase activity, i.e. a positive regulation in phorbol ester-treated cells and a negative regulation in chemoattractant-stimulated PMNs. 相似文献
99.
100.
A single injection of hexoestrol, 45 mg., is effective in suppressing lactation. Given in this way hexoestrol causes a small rise in plasma factor IX levels, of shorter duration than that produced by a customary and equally effective oral course of stilboestrol. With hexoestrol the plasma factor IX levels reverted to normal by the sixth day of the puerperium. 相似文献