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991.
Purple acid phosphatase in the walls of tobacco cells 总被引:1,自引:0,他引:1
Purple acid phosphatase isolated from the walls of tobacco cells appears to be a 220 kDa homotetramer composed of 60 kDa subunits, which is purple in color and which contains iron as its only metal ion. Although the phosphatase did not require dithiothreitol for activity and was not inhibited by phenylarsine oxide, the enzyme showed a higher catalytic efficiency (kcat/Km) for phosphotyrosine-containing peptides than for other substrates including p-nitrophenyl-phosphate and ATP. The phosphatase formed as a 120 kDa dimer in the cytoplasm and as a 220 kDa tetramer in the walls, where Brefeldin A blocked its secretion during wall regeneration. According to our double-immunofluorescence labeling results, the enzyme might be translocated through the Golgi apparatus to the walls at the interphase and to the cell plate during cytokinesis. 相似文献
992.
Nagano AJ Fukao Y Fujiwara M Nishimura M Hara-Nishimura I 《Plant & cell physiology》2008,49(6):969-980
PYK10/BGLU23 is a beta-glucosidase that is a major protein of ER bodies, which are endoplasmic reticulum (ER)-derived organelles that may be involved in defense systems. PYK10 has active and inactive forms. Active PYK10 molecules form large complexes with diameters ranging from 0.65 microm to > 70 microm. We identified three beta-glucosidases (PYK10, BGLU21 and BGLU22), five jacalin-related lectins (JALs) and a GDSL lipase-like protein (GLL) in the purified PYK10 complex. Expression levels of JALs and GLLs were lower in the nai1-1 mutant, which has no ER bodies, than in Col-0. The subcellular localization of PYK10 is predicted to be different from the localizations of JALs and GLLs. This suggests that PYK10 interacts with its partners (JALs and GLLs) when the subcellular structure is destroyed by pathogens. The PYK10 complex was found to be larger in the pbp1-1 and jal22-1 mutants than in Col-0, while it was smaller in the jal23-1, jal31-1 and jal31-2 mutants than in Col-0. These results show that two types of JALs having opposite roles regulate the size of the PYK10 complex antagonistically. We define the two types of lectins as a 'polymerizer-type lectin' and an 'inhibitor-type lectin'. Interestingly, the closest homologs of polymerizer-type lectins (JAL31 and JAL23) were inhibitor-type lectins (PBP1/JAL30 and JAL22). The pairs of polymerizer-type and inhibitor-type lectins reported here are good examples of genes that have evolved new functions after gene duplication (neofunctionalization). 相似文献
993.
994.
Katsuhiko Sakamoto Rihito Asai Atsushi Okada Isamu Shimizu 《Biological Rhythm Research》2003,34(1):61-71
To investigate the functional involvement of carotenoid in the insect circadian rhythm, we observed the effect of carotenoid depletion on the hatching patterns of the silkworm under several light conditions. When eggs were transferred from continuous light (LL) to continuous darkness (DD), an overt hatching rhythm was initiated. The first hatching peak, which was observed at 13.2 h after the transfer in the carotenoid-depleted silkworm, was reduced remarkably in both control groups (carotenoid-rich and carotenoid-depleted but with lutein supplementation), though subsequent peaks occurred with similar timing. Under LD 4 : 20, LD 12 : 12 and LD 20 :4, hatching patterns depended on the dietary carotenoid and the light intensity of the photophase. At a low light intensity, carotenoid depletion suppressed hatching as a masking effect just after light-on. Under LD 4 : 20 at a low light illumination, hatchings in the carotenoid-depleted silkworm were observed during scotophase, but few larvae hatched during scotophase in the control groups. Our findings suggest that carotenoid is not indispensable for the photoreception, formation and entrainment of the circadian hatching rhythm, but that a carotenoid-dependent process that is induced by light-off and damps out in an hour-glass mode, suppresses the hatching during darkness without affecting the circadian oscillation. The possibility that this carotenoid-dependent process is involved in the photoperiodic induction in the silkworm was discussed. 相似文献
995.
Ultrafast dynamics of bacteriorhodopsin (bR) has been extensively studied experimentally and theoretically. However, there are several contradictory results reported, indicating that its detailed dynamics and initial process have not yet been fully clarified. In this work, changes in the amplitude and phase of molecular vibration in the isomerization process of bR were real-time probed simultaneously at 128 different wavelengths through intensity modulation of the electronic transition. Systematic information on the transient change in continuous spectrum extending from 505 nm (2.45 eV) to 675 nm (1.84 eV) showed different dynamics in each spectral region reflecting the difference in the excited states and intermediates dominating the dynamics during the photoisomerization. Careful analysis of the transient spectral changes and spectrograms calculated from the vibrational real-time traces elucidated that the primary event just after photoexcitation is the deformation of the retinal configuration, which decays within 30 fs near the C=N bond in the protonated Schiff base. The intensity of C=N stretching mode starts to decrease before the initiation of the frequency modulation of the C=C stretching mode. The C=C stretching mode frequency was modulated by a coupled torsion around the C13=C14 bond, leading to the photoisomerization around the bond. This study clarified the dynamics of the C=N and C=C stretching modes working as key vibration modes in the photoisomerization of bR. Furthermore, we have elucidated the modulation and decay dynamics of the C=C stretching mode in the photoreaction starting from H (Franck-Condon excited state) followed by I (twisted excited), and J (first intermediate) states. 相似文献
996.
Prosimians (tarsiers and strepsirrhini) represent the basal lineages in primates and have a close bearing on the origin of primates. Although major lineages among anthropoidea (humans, apes and monkeys) are well represented by complete mitochondrial DNA (mtDNA) sequence data, only one complete mtDNA sequence from a representative of each of the infraorders in prosimians has been described until quite recently, and therefore we newly determined complete mtDNA sequences from 5 lemurs, 4 lorises, one tarsier and one platyrrhini. These sequences were provided to phylogenetic analyses in combination with the sequences from the 15 primates species reported to the database. The position of tarsiers among primates could not be resolved by the maximum likelihood (ML) and neighbor-joining (NJ) analyses with several data sets. As to the position of tarsiers, any of the three alternative topologies (monophyly of haplorhini, monophyly of prosimians, and tarsiers being basal in primates) was not rejected at the significance level of 5%, neither at the nucleotide nor at the amino acid level. In addition, the significant variations of C and T compositions were observed across primates species. Furthermore, we used AGY data sets for phylogenetic analyses in order to remove the effect of different C/T composition bias across species. The analyses of AGY data sets provided a medium support for the monophyly of haplorhini, which might have been screened by the variation in base composition of mtDNA across species. To estimates the speciation dates within primates, we analyzed the amino acid sequences of mt-proteins with a Bayesian method of Thorne and Kishino. Divergence dates were estimated as follows for the crown groups: about 35.4 million years ago (mya) for lorisiformes, 55.3 mya for lemuriformes, 64.5 mya for strepsirrhini, 70.1 mya for haplorhini and 76.0 mya for primates. Furthermore, we reexamined the biogeographic scenarios which have been proposed for the origin of strepsirrhini (lemuriformes and lorisiformes) and for the dispersal of the lemuriformes and lorisiformes. 相似文献
997.
A new method for the analysis of domain movements in large, multichain, biomolecular complexes is presented. The method is applicable to any molecule for which two atomic structures are available that represent a conformational change indicating a possible domain movement. The method is blind to atomic bonding and atom type and can, therefore, be applied to biomolecular complexes containing different constituent molecules such as protein, RNA, or DNA. At the heart of the method is the use of blocks located at grid points spanning the whole molecule. The rotation vector for the rotation of atoms from each block between the two conformations is calculated. Treating components of these vectors as coordinates means that each block is associated with a point in a “rotation space” and that blocks with atoms that rotate together, perhaps as part of the same rigid domain, will have colocated points. Thus a domain can be identified from the clustering of points from blocks that span it. Domain pairs are accepted for analysis of their relative movements in terms of screw axes based upon a set of reasonable criteria. Here, we report on the application of the method to biomolecules covering a considerable size range: hemoglobin, liver alcohol dehydrogenase, S‐Adenosylhomocysteine hydrolase, aspartate transcarbamylase, and the 70S ribosome. The results provide a depiction of the conformational change within each molecule that is easily understood, giving a perspective that is expected to lead to new insights. Of particular interest is the allosteric mechanism in some of these molecules. Results indicate that common boundaries between subunits and domains are good regions to focus on as movement in one subunit can be transmitted to another subunit through such interfaces. Proteins 2009. © 2008 Wiley‐Liss, Inc. 相似文献
998.
999.
Electron shuttles in biotechnology 总被引:1,自引:0,他引:1
1000.
Atsushi Kameda Eugene‐Hayato Morita Kazumasa Sakurai Hironobu Naiki Yuji Goto 《Protein science : a publication of the Protein Society》2009,18(8):1592-1601
In patients with dialysis‐related amyloidosis, β2‐microglobulin (β2‐m) is a major structural component of amyloid fibrils. It has been suggested that the partial unfolding of β2‐m is a prerequisite to the formation of amyloid fibrils, and that the folding intermediate trapped by the non‐native trans‐Pro32 isomer leads to the formation of amyloid fibrils. Although clarifying the structure of this refolding intermediate by high resolution NMR spectroscopy is important, this has been made difficult by the limited lifetime of the intermediate. Here, we studied the structure of the refolding intermediate using a combination of amino acid selective labeling with wheat germ cell‐free protein synthesis and NMR techniques. The HSQC spectra of β2‐ms labeled selectively at either phenylalanine, leucine, or valine enabled us to monitor the structures of the refolding intermediate. The results suggested that the refolding intermediate has an overall fold and cores similar to the native structure, but contains disordered structures around Pro32. The fluctuation of the β‐sheet regions especially the last half of the βB strand and the first half of the βE strand, both suggested to be important for amyloidogenicity, may transform β2‐m into an amyloidogenic structure. 相似文献