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81.
82.
We studied the synthesis and binding of phycoerythrin and its associated linkers to the phycobilisome (PBS) in Rhodella violacea (Kornmann) Wehrmeyer and compared the effects of high light and translation inhibitors on these processes. Rhodella violacea has a simple hemidiscoidal PBS structure with a well-known composition. The number of PBSs per cell decreases when irradiance is increased, and at higher irradiances the rods are shortened with a specific loss of the terminal hexamer of phycoerythrin (PE) and its associated linker. To test whether or not the observed variations were due to a coordination between the expression of the chloroplast-encoded PE and the nuclear-encoded linkers, we inhibited the expression of the chloroplast genes by the translation inhibitor chloramphenicol. In the few PBSs synthesized, the linker associated to the terminal PE hexamer was missing while that associated with the intermediate PE hexamer was still present. The inhibition by cycloheximide of the translation of the nuclear-encoded linkers did not influence the synthesis of the chloroplast-encoded phycobiliproteins. The absence of linkers prevented the formation of PE hexamers and their binding to the PBSs. We therefore propose the existence of two levels of regulation for PE and associated linkers: the intermediate PE hexamer and associated linker are always present even though their amount is reduced when irradiance is increased. In contrast, the terminal hexamer of PE and its associated linker are no longer present under high light. Their absence can be due to a feedback control between the level of PE and the synthesis of the linker: when the level of PE is lowered below a given value by the action of light on the chloroplast, a signal coming from the chloroplast reaches the nucleus and the synthesis of the linker is repressed. There is no sign of nuclear regulation of the synthesis of PE, but the nuclear-encoded linkers have a structural role in the formation of PE hexamers. 相似文献
83.
The modification effects on the absorption and cirular dichroic (CD) spectra of the isolated B800-860 antenna complex of Rhodocyclus tenuis by a number of proteolytic enzymes were investigated. The chymotrypsin modifications of the B800-860 complex led to an about 40% decrease of the 860-nm band and a blue-shift to 841 nm. The biphasic CD signal related to the B860 BChl disappeared and a new double CD signal with a zero-crossing point at 842 nm appeared. These absorption and CD spectral changes suggested that a B800-841 complex resulted after chymotrypsin digestion. The polypeptide components of the chymotrypsin-modified B800-860 complex were separated by reverse-phase chromatography, and their amino acid sequences determined by protein sequencing and mass spectrometry. Sequence analyses showed that the C-terminal 25 residues of the B800-860- polypeptide and the C-terminal 8 residues of the B800-860- polypeptide were cleaved by chymotrypsin, and the remaining , polypeptide fragments apparently form the structural basis for the newly-formed B800-841 complex. No significant spectral change was observed from exposing the isolated B800-860 complex to trypsin, carboxypeptidase A and the combination of carboxypeptidase A and carboxypeptidase B. Short-term proteinase K incubation of the B800-860 complex of Rc. tenuis led to a preferential decrease of the 860-nm absorbance band and its related CD signals, as compared to the 800-nm absorbance and CD bands, suggesting that the C-terminal portions of the antenna polypeptides are possibly exposed to the exterior of the B800-860 complex micelles. Whereas, long-term proteinase K digestion resulted in the spectral collapse of the B800-860 complex and the release of free BChls. Our proteolysis experiments support the hypothesis that the C-terminal portions of the antenna polypeptides play a key role in the redshift and strong molar extinction of the Qy band of the B850 BChls.Abbreviations B800-860
light-harvesting complex with the absorption maxima (Qy) at 800 nm and 860 nm
- B800-860-
-, polypeptide of the B800-860 complex
- CD
circular dichroism
- Deriphat-160
disodium Nlauryl--iminodipropionate
- FT
Fourier transform
- LH
light-harvesting
- near-IR
near infra-red
- OG
n-Octyl--glucoside
- PTH
phenylthiohydantoin
-
Rb.
Rhodobacter
-
Rc.
Rhodocyclus
-
Rp.
Rhodopseudomonas
-
Rsp
Rhodospirillum
- DSM
Deutsche Sammlung für Mikroorganismen 相似文献
84.
K. Muthuchelian C. Murugan R. Harigovindan N. Nedunchezhian G. Kulandaivelu 《Biologia Plantarum》1995,37(3):355-362
In seedlings of the tropical tree speciesErythrina variegata Lam. andHardwickia binata Roxb. exposed to different acidic mist (H2SO4, pH 5, 3 and 2) for 5 d significant reduction in seedling growth, biomass accumulation and14CO2 fixation were determined. In isolated chloroplasts a decrease in the activities of photosystem 2 and whole electron transport
chain was observed only at pH 3 and 2, but no significant change in photosystem 1 activity was observed. SDS-PAGE analysis
of crude leaf extracts of ribulose 1,5-bisphosphate carboxylase (RuBPC) indicated a significant loss of 55 and 15 kDa polypeptides
at pH 2 inErythrina. The reduction in the RuBPC activity in seedlings grown under acidic mists correlated well with CO2 fixation. 相似文献
85.
In six rice cultivars the relative amounts of 55, 26–28 and 15 kDa polypeptides were mostly lower in plants grown for 15 d
under low irradiance than in plants grown under saturating irradiance. This decline in the polypeptides, especially in those
related to light-harvesting chlorophyll proteins, was accompanied with a decrease in the whole chain electron transport and
the photosystem 2 activity. 相似文献
86.
Chloroflexus aurantiacus was grown phototrophically in the presence of 60 µg of 2-hydroxybiphenyl (HBP) per ml, which inhibited the formation of colored carotenoids up to about 90%, while bacteriochlorophyll (BChl) c formation and phototrophic growth were not significantly influenced. When the HBP concentration was increased, the latter two processes became inhibited, yet, no further inhibition of carotenoid formation was possible. The typical shape of chlorosomes was not affected after growth in the presence of 60 µg of HBP per ml. However, the chlorosome dimensions were slightly decreased. Chlorosome preparations from carotenoid-deficient cultures lacked significant amounts of colored carotenoids and exhibited lower buoyant densities than chlorosomes from uninhibited control cultures. As compared on a BChl c basis, the relative contents of the two larger chlorosomal polypeptides of 10.8 and 15.5 kDa (apparent Mr= 11000 and 18000) were not affected by HBP, while formation of the 5.7 kDa (Mr= 3700) polypeptide was inhibited by 50%. The data suggest that, in C. aurantiacus, colored carotenoids are largely dispensable for phototrophic growth and chlorosome formation. Moreover, chlorosome formation and BChl c incorporation into chlorosomes in the absence of about half of the regular amount of the 5.7 kDa polypeptide excludes a constant relationship between these parameters. 相似文献
87.
The counterreceptor binding site of human CD2 exhibits an extended surface patch with multiple conformations fluctuating with millisecond to microsecond motions. 总被引:3,自引:1,他引:2 下载免费PDF全文
D. F. Wyss K. T. Dayie G. Wagner 《Protein science : a publication of the Protein Society》1997,6(3):534-542
We have used 15N NMR relaxation experiments to probe, for the glycosylated human CD2 adhesion domain, the overall molecular motion, as well as very fast nanosecond-picosecond (ns-ps) and slow millisecond-microsecond (ms-microsecond) internal motions. Using a novel analysis method that considers all residues, we obtained a correlation time for the overall motion of 9.5 +/- 0.3 ns. Surprisingly, we found a large contiguous patch of residues in the counterreceptor (CD58) binding site of human CD2 exhibiting slow conformational exchange motions (ms-microsecond). On the other hand, almost none of the residues of the CD58 binding side display fast (ns-ps) internal motions of amplitudes larger than what is seen for well-ordered regions of the structure. Residues close to the N-glycosylation site, and the first N-acetylglucosamine of the high mannose glycan are as rigid as the protein core. Residues conserved in the immunoglobulin superfamily V-set domain are generally very rigid. 相似文献
88.
Clathrin-coated vesicles, identified by negative staining with uranyl acetate, were purified from Chlamydomonas rein-hardtii. Isolated coated vesicles had diameters ranging from 70 to 140 nm (mean diameter±SD of 95±17 nm, n=300). These vesicles were markedly heterogeneous in both density and surface charge, as indicated by equilibrium density sedimentation and elution from anion-exchange columns. Highly-purified coated-vesicle fractions contained 2 major polypeptides, identified as the clathrin heavy chain (185 kDa) and the clathrin light chain (40 kDa). Chlamydomonas clathrin heavy chain cross-reacts weakly with an antibody against bovine brain clathrin heavy chain. Coat stability in several buffers was compared to that of bovine brain coated vesicles. Stability was similar, except for a greater stability of Chlamydomonas coated vesicles in 0.5 M Tris at pH 7.0. 相似文献
89.
90.
J. G. Boothe D. B. Walden 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,77(4):495-500
Summary Variation in polypeptide synthesis was examined in developing maize embryos of two inbred and two hybrid genotypes. Multivariate analyses were used to evaluate the variation among two-dimensional, electrophoretic separations of polypeptides. Several features of the data set were revealed. Similar developmental patterns were exhibited by all genotypes and no evidence was obtained for differential rates of development for inbreds and hybrids. The differential synthesis of two subsets of polypeptides during embryo development was observed. The multivariate methods employed in this study were a valuable aid in interpreting the results from a large and complex data set. 相似文献