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41.
42.
The Escherichia coli metD locus encodes an ABC transporter which includes Abc (MetN), YaeE (MetI), and YaeC (MetQ) 总被引:1,自引:0,他引:1
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We report that the genes abc, yaeC, and yaeE comprise metD, an Escherichia coli locus encoding a DL-methionine uptake system. MetD is an ABC transporter with Abc the ATPase, YaeE the permease, and YaeC the likely substrate binding protein. Expression of these genes is regulated by L-methionine and MetJ, a common repressor of the methionine regulon. We propose to rename abc, yaeE, and yaeC as metN, metI, and metQ, respectively. 相似文献
43.
The relationship between molecular architecture and the nature of interactions with lipid bilayers has been studied for a series of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers using small-angle X-ray scattering (SAXS) and thermal analysis (differential scanning calorimetry, DSC). The number of molecular repeat units in the hydrophobic poly(propylene oxide), PPO, block has been found to be a critical determinant of the nature of triblock copolymer-lipid bilayer association. For dimyristoyl-sn-glycero-3-phosphocholine (DMPC)-based biomembrane structures, polymers possessing a PPO chain length commensurate with the acyl chain dimensions of the lipid bilayer yield highly ordered, swollen lamellar structures consistent with well-integrated (into the lipid bilayer) PPO blocks. Triblock copolymers of lesser PPO chain length yield materials with structural characteristics similar to a simple dispersion of DMPC in water. Increasing the concentration (from 4 to 12 mol %) of well-integrated triblock copolymers enhances the structural ordering of the lamellar phase, while concentrations exceeding 16 mol % result in the formation of a hexagonal phase. Examination of temperature-induced changes in the structure of these mesophases (complex fluids) reveals that if the temperature is reduced sufficiently, all compositions exclude polymer and thus exhibit the characteristic SAXS pattern for hydrated DMPC bilayers. Increasing the temperature promotes better insertion of the polymers possessing PPO chain lengths sufficient for membrane insertion. No temperature-induced structural changes are observed in compositions prepared with PEO-PPO-PEO polymers that feature PPO length insufficient to permit full incorporation into the lipid bilayer. 相似文献
44.
The impact of drought on plant growth and yield has been widely studied and is considered a major limitation to crops reaching yield potential. Less known is the impact of water deficit on the nutritional quality of the resulting yield. This study characterised the impact of water deficit on carbon assimilation, modelled water use efficiency from carbon isotope discrimination and analysed the concentration of mineral nutrients, amino acids and sugars in leaf, phloem and pod pools collected from Phaseolus vulgaris L. (common bean) grown in a controlled environment. Water deficit led to an isohydric response, impacting on carbon isotope abundance in all tissues though not translating to any significant treatment differences in water use efficiency or nutrient content in tissues over the course of plant development. The results obtained in this study demonstrate that nutrient content of P. vulgaris yield was not impacted by the availability of water. The absence of significant changes in the nutrient content of individual seeds highlights the plasticity of developing reproductive tissue to changes in whole plant water availability. 相似文献
45.
A Single-Ring Mitochondrial Chaperonin (Hsp60-Hsp10) Can Substitute for GroEL-GroES In Vivo 总被引:2,自引:0,他引:2
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Kre L. Nielsen Neil McLennan Millicent Masters Nicholas J. Cowan 《Journal of bacteriology》1999,181(18):5871-5875
Chaperonins participate in the facilitated folding of a variety of proteins in vivo. To see whether the same spectrum of target proteins can be productively folded by the double-ring prokaryotic chaperonin GroEL-GroES and its single-ring human mitochondrial homolog, Hsp60-Hsp10, we expressed the latter in an Escherichia coli strain engineered so that the groE operon is under strict regulatory control. We found that expression of Hsp60-Hsp10 restores viability to cells that no longer express GroEL-GroES, formally demonstrating that Hsp60-Hsp10 can carry out all essential in vivo functions of GroEL-GroES. 相似文献
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47.
Robert W. Ficken Millicent S. Ficken Jack P. Hailman 《Ethology : formerly Zeitschrift fur Tierpsychologie》1978,46(1):43-57
To see if genetic differences correlate with differences in agonistic behavior, 225 encounters within and between color morphs of the white-throated sparrow (Zonotrichia albicollis) were observed in feeding groups of different sizes and morphic compositions. Tan morphs lack the M chromosome that replaces either of two chromosomes in the white morph. The data were analysed using quantitative models accounting for the proportions of morphs present, and the principal finding was that morphs are equally frequent recipients of aggression but the white morph was the aggressor more frequently than by chance expectation — regardless of the morph of the recipient, the size of the group or the morphic composition of the group. 相似文献
48.
49.
Regulation of plasmid R1 replication: PcnB and RNase E expedite the decay of the antisense RNA, CopA 总被引:6,自引:1,他引:5
Fredrik Söderbom Uta Binnie Millicent Masters & E. Gerhart H. Wagner 《Molecular microbiology》1997,26(3):493-504
The replication frequency of plasmid R1 is controlled by an unstable antisense RNA, CopA, which, by binding to its complementary target, blocks translation of the replication rate-limiting protein RepA. Since the degree of inhibition is directly correlated with the intracellular concentration of CopA, factors affecting CopA turnover can also alter plasmid copy number. We show here that PcnB (PAP I — a poly(A)polymerase of Escherichia coli ) is such a factor. Previous studies have shown that the copy number of ColE1 is decreased in pcnB mutant strains because the stability of the RNase E processed form of RNAI, the antisense RNA regulator of ColE1 replication, is increased. We find that, analogously, the twofold reduction in R1 copy number caused by a pcnB lesion is associated with a corresponding increase in the stability of the RNase E-generated 3' cleavage product of CopA. These results suggest that CopA decay is initiated by RNase E cleavage and that PcnB is involved in the subsequent rapid decay of the 3' CopA stem-loop segment. We also find that, as predicted, under conditions in which CopA synthesis is unaffected, pcnB mutation reduces RepA translation and increases CopA stability to the same extent. 相似文献
50.
Limakatso Lebina Noah Taruberekera Minja Milovanovic Karin Hatzold Miriam Mhazo Cynthia Nhlapo Nkeko Tshabangu Mmatsie Manentsa Victoria Kazangarare Millicent Makola Scott Billy Neil Martinson 《PloS one》2015,10(9)