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111.
Awazuhara M Kim H Hayashi H Chino M Kim SG Fujiwara T 《Bioscience, biotechnology, and biochemistry》2002,66(8):1751-1754
The application of glutathione to immature soybean cotyledons reduced the accumulation of the beta subunit of beta-conglycinin, and increased the accumulation of most glycinins. Both reduced and oxidized forms of glutathione had these effects. The application of an inhibitor of glutathione synthesis, buthionine sulfoximine, increased accumulation of beta subunit. These results suggest that glutathione is important in affecting the composition of seed storage proteins. 相似文献
112.
We examined morphological changes in the first-formed protoxylem vessels in Arabidopsis seedlings. Between 2.5 and 8 days after imbibition, mean hypocotyl and root length increased 1.52 and 23.3 times, respectively. In the 2.5-day-old seedlings, two continuous protoxylem vessels were present in the hypocotyl-root axis. In the 8-day-old upper hypocotyls, six protoxylem vessels were observed, and in the lower hypocotyls, four protoxylem vessels and one or two metaxylem vessels were observed. In the 8-day-old roots, there were two protoxylem vessels and two or three metaxylem vessels. Two protoxylem vessels in the hypocotyls connected to two metaxylem vessels in the roots of 8-day-old seedlings. At the 0.3-mm part below the hypocotyl-root boundary, the mean intervals of neighboring annular secondary wall thickenings in protoxylem vessels in 8-day-old roots were 12.9% larger than those in 2.5-day-old roots. In more apical parts of 8-day-old roots, the mean intervals fluctuated between 1.71 and 2.29 microm. In 8-day-old seedlings, metaxylem vessels were formed between 0.4 mm above the hypocotyl-root boundary and 17 mm below the boundary. The intervals in these regions were not extended so much as protoxylem vessels were collapsed. The first-formed protoxylem vessels presumably retain their water-conductive function after metaxylem formation. 相似文献
113.
Ishida H Nakashima K Kumaki Y Nakata M Hikichi K Yazawa M 《Journal of biomolecular NMR》2002,23(4):323-324
Calmodulin (CaM) is a small Ca2+-binding protein, which has been found in all of eucaryotic cells examined. CaMs isolated from various species have highly conserved amino acid sequence (more than 90% identical), and show the same biological functions. CaM isolated from the baker's yeast (Saccharomyces cerevisiae) (yCaM), however, shares only 60% identity in the amino acid sequence with CaM from vertebrate, and shows quite distinct conformational and biochemical properties compared with those of CaM from other species. The conformational details of yCaM, however, have not been revealed yet. We achieved the chemical shift assignments of yCaM (146 amino acids) in the apo-state using uniformly 15N- and 13C-labeled protein. Consequently, the resonances of 95% atoms in the backbone amides were successfully assigned. 相似文献
114.
In this study, a new method is proposed to estimate the torque-vector directions of each shoulder muscle. The method is based on a multiple regression model that reconstructs shoulder torque, which is calculated from the hand force and posture, from the surface EMG of many muscles recorded simultaneously. The torque-vector directions of eleven shoulder muscles of four subjects were obtained at up to 30 different arm postures with this method. The mean confidence interval (p < 0.05) of the estimated torque-vector direction of each subject was 7.7-10.6 degrees. The correlation coefficient between the measured shoulder torque and reconstructed shoulder torque was between 0.76-0.84. The results for majority of the muscles were in accordance with previous studies, and reasonable from the viewpoint of anatomy. The torque-vector directions of a muscle, which are estimated with this method, have more of a functional meaning than a pure anatomical or mechanical one. These indicate the direction of the shoulder torque accompanying the muscle activation for a normal shoulder action that involves the cooperative contraction of many muscles. 相似文献
115.
The phase-resetting experiment was applied to human periodic finger tapping to understand how its rhythm is controlled by
the internal neural clock that is assumed to exist. In the experiment, the right periodic tapping movement was disturbed transiently
by a series of left finger taps in response to impulsive auditory cues presented randomly at various phases within the tapping
cycle. After each left finger tap, the original periodic tapping was reestablished within several tapping cycles. Influences
of the disturbance on the periodic right finger tapping varied depending on the phase of the periodic right finger tapping
at which each left finger tap was made. It was confirmed that the periodic tapping was disturbed not by the auditory cues
but by the left finger taps. Based on this fact, in this paper each single left tap was considered as the stimulus, and the
phase of the periodic tapping of the right index finger when the left tap was executed as the phase of the stimulus. Responses
of the neural activities (magnetoencephalography, MEG), the tapping movement, and the corresponding muscle activities (electromyography)
were simultaneously measured. Phase-resetting curves (PRCs) representing the degree of phase reset as a function of the phase
of the stimulus were obtained both for the left sensorimotor cortex MEG response and for the right index finger tapping response.
The shapes of both PRCs were similar, suggesting that the phase reset of the left sensorimotor cortex activities and that
of the finger tapping rhythm were the same. Four out of eight subjects showed type-0 reset in Winfree's definition, and the
others showed type-1 reset. For general limit-cycle oscillators, type-0 reset is obtained for relatively strong perturbations
and type 1 for weak perturbations. It was shown that the transient response of MEG to the single left tap stimuli in type-0
subjects, where the phase was progressively reset, were different from those in type-1 subjects. Based on detailed analysis
of the differences, a neural network model for the phase reset of the tapping rhythm is proposed.
Received: 10 February 2000 / Accepted in revised form: 15 January 2002 相似文献
116.
Nishigaki R Shinohara T Toda T Omori A Ichinose S Itoh M Shirayoshi Y Kurimasa A Oshimura M 《Biochemical and biophysical research communications》2002,295(1):112-118
An extra copy of human chromosome 21 (Chr 21) causes Down syndrome (DS), which is characterized by mental retardation and congenital heart disease (CHD). Chimeric mice containing Chr 21 also exhibit phenotypic traits of DS including CHD. In this study, to identify genes contributing to DS phenotypes, we compared the overall protein expression patterns in hearts of Chr 21 chimeras and wild type mice by two-dimensional electrophoresis. The endogenous mouse atrial specific isoform of myosin light chain-2 (mlc-2a) protein was remarkably downregulated in the hearts of chimeric mice. We also confirmed that the human MLC-2A protein level was significantly lower in a human DS neonate heart, as compared to that of a normal control. Since mouse mlc-2a is involved in heart morphogenesis, our data suggest that the downregulation of this gene plays a crucial role in the CHD observed in DS. The dosage imbalance of Chr 21 has a trans-acting effect which lowers the expression of other genes encoded elsewhere in the genome. 相似文献
117.
CPI17 and myosin binding subunit of type 1 protein phosphatase (MBS) are the regulators of myosin light chain phosphatase (MLCP). The function of both regulators is controlled by phosphorylation. The phosphorylation of CPI17 at Thr38 significantly enhances the inhibitory activity of CPI17 and the phosphorylation at Thr641 of MBS decreases the MLCP activity. Here, we found that p21-activated protein kinase (PAK) phosphorylates both CPI17 at Thr38 and MBS at Thr641. For CPI17, PAK specifically phosphorylated at Thr38, since the mutation of Thr38 to Ala completely abolished the phosphorylation. On the other hand, PAK phosphorylated Thr641 but not Thr799 of MBS, the site phosphorylated by Rho kinase. Because PAK phosphorylates MBS more than 1 mol/mol, it is anticipated that PAK also phosphorylates other sites in addition to Thr641. CPI17 phosphorylation induced by PAK significantly enhanced the inhibitory activity of CPI17. On the other hand, the phosphorylation of MBS by PAK also decreased the MLCP activity. These results raise the possibility that the PAK pathway plays a role in MLCP regulation. 相似文献
118.
So Nishikawa Kazuaki Homma Yasunori Komori Mitsuhiro Iwaki Tetsuichi Wazawa Atsuko Hikikoshi Iwane Junya Saito Reiko Ikebe Eisaku Katayama Toshio Yanagida Mitsuo Ikebe 《Biochemical and biophysical research communications》2002,290(1):311-317
Among a superfamily of myosin, class VI myosin moves actin filaments backwards. Here we show that myosin VI moves processively on actin filaments backwards with large ( approximately 36 nm) steps, nevertheless it has an extremely short neck domain. Myosin V also moves processively with large ( approximately 36 nm) steps and it is believed that myosin V strides along the actin helical repeat with its elongated neck domain that is critical for its processive movement with large steps. Myosin VI having a short neck cannot take this scenario. We found by electron microscopy that myosin VI cooperatively binds to an actin filament at approximately 36 nm intervals in the presence of ATP, raising a hypothesis that the binding of myosin VI evokes "hot spots" on actin filaments that attract myosin heads. Myosin VI may step on these "hot spots" on actin filaments in every helical pitch, thus producing processive movement with 36 nm steps. 相似文献
119.
The inhibitory properties of TIMP-4 for matrix metalloproteinases (MMPs) were compared to those of TIMP-1 and TIMP-2. Full-length human TIMP-4 was expressed in E. coli, folded from inclusion bodies, and the active component was purified by MMP-1 affinity chromatography. Progress curve analysis of MMP inhibition by TIMP-4 indicated that association rate constants (k(on)) and inhibition constants (K(i)) were similar to those for other TIMPs ( approximately 10(5) M(-)(1) s(-)(1) and 10(-)(9)-10(-)(12) M, respectively). Dissociation rate constants (k(off)) for MMP-1 and MMP-3 determined using alpha(2)-macroglobulin to capture MMP dissociating from MMP-TIMP complexes were in good agreement with values deduced from progress curves ( approximately 10(-)(4) s(-)(1)). K(i) and k(on) for the interactions of TIMP-1, -2, and -4 with MMP-1 and -3 were shown to be pH dependent. TIMP-4 retained higher reactivity with MMPs at more acidic conditions than either TIMP-1 or TIMP-2. Molecular interactions of TIMPs and MMPs investigated by IAsys biosensor analysis highlighted different modes of interaction between proMMP-2-TIMP-2 (or TIMP-4) and active MMP-2-TIMP-2 (or TIMP-4) complexes. The observation that both active MMP-2 and inactive MMP-2 (with the active site blocked either by the propeptide or a hydroxamate inhibitor) have essentially identical affinities for TIMP-2 suggests that there are two TIMP binding sites on the hemopexin domain of MMP-2: one with high affinity that is involved in proMMP-2 or hydroxamate-inhibited MMP-2; and the other with low affinity involved in formation of the complex of active MMP-2 and TIMP-2. Similar models of interaction may apply to TIMP-4. The latter low-affinity site functions in conjunction with the active site of MMP-2 to generate a tight enzyme-inhibitor complex. 相似文献
120.
Shinji Onoe Susumu Ando Mitsuo Ataka Kazuhiko Ishikawa 《Biochemical and biophysical research communications》2002,290(3):994-997
New hyperthermostable aminopeptidase from the hyperthermophilic archaeon Pyrococcus horikoshii has acylamino acid releasing (deblocking) activity for acyl (blocked) peptides. Such an enzyme can be used for N-terminal sequencing of acyl peptides. To clarify the active site of the deblocking aminopeptidase, we prepared three mutants in which one of the three possible active site amino acid residues (Asp or Glu) was replaced with their amide derivatives. Activity and cobalt ion dependence of these mutants were examined and compared with those of the native enzyme. The results suggest that all the three possible residues (Asp173, Glu205, and Glu206) participate in the catalytic activity through binding with the cobalt ion. 相似文献