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1.
The desulfurization activity of the resting cells of Gordona sp. CYKS1 was strongly depended on harvest time and the highest value when the cells had been harvested in the early growth phase (0.12 mg sulfur g–1 cell–1 h–1). For the model oil, hexadecane containing dibenzothiophene, the specific desulfurization rate decreased as the reaction proceeded. Both the specific and the volumetric desulfurization rates were not significantly affected by the aqueous-to-oil phase ratio. The diesel oils, light gas oil and a middle distillate unit feed were desulfurized at higher rates (ca. 0.34 mg sulfur g–1 cell–1 h–1) than the model oil (0.12 mg sulfur g–1 cell–1 h–1). 相似文献
2.
Yi-Hua Wu Chia-Pei Chang Chin-I Chien Yi-Kuan Tseng Chien-Chia Wang 《Molecular and cellular biology》2013,33(17):3515-3523
The yeast Saccharomyces cerevisiae possesses two distinct glycyl-tRNA synthetase (GlyRS) genes: GRS1 and GRS2. GRS1 is dually functional, encoding both cytoplasmic and mitochondrial activities, while GRS2 is dysfunctional and not required for growth. The protein products of these two genes, GlyRS1 and GlyRS2, are much alike but are distinguished by an insertion peptide of GlyRS1, which is absent from GlyRS2 and other eukaryotic homologues. We show that deletion or mutation of the insertion peptide modestly impaired the enzyme''s catalytic efficiency in vitro (with a 2- to 3-fold increase in Km and a 5- to 8-fold decrease in kcat). Consistently, GRS2 can be conveniently converted to a functional gene via codon optimization, and the insertion peptide is dispensable for protein stability and the rescue activity of GRS1 at 30°C in vivo. A phylogenetic analysis further showed that GRS1 and GRS2 are paralogues that arose from a gene duplication event relatively recently, with GRS1 being the predecessor. These results indicate that GlyRS2 is an active enzyme essentially resembling the insertion peptide-deleted form of GlyRS1. Our study suggests that the insertion peptide represents a novel auxiliary domain, which facilitates both productive docking and catalysis of cognate tRNAs. 相似文献
3.
Ciliated tracheal epithelia cell cultures were investigated immunocytochemically with anti-tubulin and colloidal gold. When rabbit tracheal cultures were fixed in paraformaldehyde, treated with acetone, anti-tubulin and a second antibody coupled to FITC, fluorescence was associated with cytoskeletal and axonemal microtubules. Cilia covering the apical surface of the ciliated tracheal cells fluoresced very brightly thus facilitating identification of this cell type. Electron microscopy of tracheal cultures fixed as above, treated with Triton-X 100 and incubated in anti-tubulin and protein A coupled to colloidal gold resulted in the highly specific localization of tubulin in ciliary axonemes and basal bodies. Omission of primary or secondary antibody resulted in extremely low levels of fluorescence while no colloidal gold particles could be detected in cultures at the electron microscopy level when rabbit anti-tubulin was omitted. 相似文献
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5.
James B Munro Roger B Altman Chang‐Shung Tung Kevin Y Sanbonmatsu Scott C Blanchard 《The EMBO journal》2010,29(4):770-781
A key intermediate in translocation is an ‘unlocked state’ of the pre‐translocation ribosome in which the P‐site tRNA adopts the P/E hybrid state, the L1 stalk domain closes and ribosomal subunits adopt a ratcheted configuration. Here, through two‐ and three‐colour smFRET imaging from multiple structural perspectives, EF‐G is shown to accelerate structural and kinetic pathways in the ribosome, leading to this transition. The EF‐G‐bound ribosome remains highly dynamic in nature, wherein, the unlocked state is transiently and reversibly formed. The P/E hybrid state is energetically favoured, but exchange with the classical P/P configuration persists; the L1 stalk adopts a fast dynamic mode characterized by rapid cycles of closure and opening. These data support a model in which P/E hybrid state formation, L1 stalk closure and subunit ratcheting are loosely coupled, independent processes that must converge to achieve the unlocked state. The highly dynamic nature of these motions, and their sensitivity to conformational and compositional changes in the ribosome, suggests that regulating the formation of this intermediate may present an effective avenue for translational control. 相似文献
6.
Fang Chang An Yan Li-Na Zhao Wei-Hua Wu Zhenbiao Yang 《植物学报(英文版)》2007,49(8):1261-1270
A tip-focused Ca^2+ gradient is tightly coupled to polarized pollen tube growth, and tip-localized influxes of extracellular Ca^2+ are required for this process. However the molecular identity and regulation of the potential Ca^2+ channels remains elusive. The present study has implicated CNGC18 (cyclic nucleotide-gated channel 18) in polarized pollen tube growth, because its overexpression induced wider and shorter pollen tubes. Moreover, CNGC18 overexpression induced depolarization of pollen tube growth was suppressed by lower extracellular calcium ([Ca^2+]ex). CNGC18-yellow fluorescence protein (YFP) was preferentially localized to the apparent post-Golgi vesicles and the plasma membrane (PM) in the apex of pollen tubes. The PM localization was affected by tip-localized ROP1 signaling. Expression of wild type ROP1 or an active form of ROP1 enhanced CNGC18-YFP localization to the apical region of the PM, whereas expression of RopGAP1 (a ROP1 deactivator) blocked the PM localization. These results support a role for PM-Iocalized CNGC18 in the regulation of polarized pollen tube growth through its potential function in the modulation of calcium influxes. 相似文献
7.
The urinary bladder of euryhaline teleost is an important osmoregulatory organ which absorbs Na+, Cl-, and water from urine. Using patch clamp technique, single stretch-activated channels, which were permeable to K+ and Na+ (PNa/PK approximately 0.75) and had conductances of 55 and 116 pS, were studied. In excised, inside-out patches which were voltage-clamped in the physiological range of membrane potential, the single-channel open probability (Po) was low (approximately 0.02), and increased to a maximum of 0.9 with applied pipette suction. Single-channel conductance also increased with suction. The channels showed adaptation to applied suction and relaxed to a steady-state activity about 20 seconds after application of suction. The Po increased up to 0.9 with strong membrane depolarization (Vm = 0 to +80 mV); however, there was little dependence of Po on membrane potential in the physiological range. The kinetic data suggest that there is one conducting state and at least two non-conducting states of the channel. The open-time constant increased with suction but remained unchanged with membrane potential (Vm = -70 to +60 mV). The mean closed-time of the channel decreased with suction and membrane depolarization. These results demonstrate the presence of a non-selective monovalent cation channel which may be involved in cell volume regulation in the goby urinary bladder. Additionally, this channel may function as an enhancer of Na+ influx and K+ efflux across the bladder cell as part of transepithelial ion transport if it is located in apical membrane. 相似文献
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9.
The onset of incubation varies in birds, with many species beginning incubation prior to clutch completion. Here we examine whether early onset is more likely to occur during high temperatures, a critical prediction of the egg-viability hypothesis, which suggest that birds begin incubation prior to clutch completion in order to maintain egg-viability. We examined onset of incubation in tree swallows Tachycineta bicolor at two locations at the extremes of their breeding range, Alaska and Tennessee. A majority of individuals (68%) began incubation prior to clutch completion. While females in Tennessee were more likely to begin incubation early, there was no difference between sites when differences in temperatures inside nestboxes were controlled in analyses. Rather, early onset of incubation was predicted by the proportion of daily temperatures above physiological zero during laying, a critical prediction of the egg viability hypothesis. Both warm weather and early onset led to shorter incubation periods and increased levels of hatching asynchrony. We found no effect of timing of nesting, female body condition index or clutch size on the probability of beginning incubation prior to clutch completion. Our results are consistent with the egg viability hypothesis, not consistent with a threshold clutch size rule, and do not support the hurry-up hypothesis, that individuals breeding later in the season would begin incubation early to reduce the time spent nesting. Overall, our results suggest that broad scale geographic differences in incubation behaviour may be explained by individual-level responses to environmental conditions. 相似文献
10.