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961.
Archaea-specific D-family DNA polymerase forms a heterotetramer consisting of two large polymerase subunits and two small exonuclease subunits. We analyzed the structure of the N-terminal 200 amino-acid regulatory region of the small subunit by NMR and revealed that the N-terminal ∼70 amino-acid region is folded. The structure consists of a four-α-helix bundle including a short parallel β-sheet, which is similar to the N-terminal regions of the B subunits of human DNA polymerases α and ε, establishing evolutionary relationships among these archaeal and eukaryotic polymerases. We observed monomer-dimer equilibrium of this domain, which may be related to holoenzyme architecture and/or functional regulation. 相似文献
962.
Ryusuke Yokoyama Yohei Uwagaki Hiroki Sasaki Taro Harada Yuji Hiwatashi Mitsuyasu Hasebe Kazuhiko Nishitani 《The Plant journal : for cell and molecular biology》2010,64(4):645-656
This comprehensive overview of the xyloglucan endotransglucosylase/hydrolase (XTH) family of genes and proteins in bryophytes, based on research using genomic resources that are newly available for the moss Physcomitrella patens, provides new insights into plant evolution. In angiosperms, the XTH genes are found in large multi‐gene families, probably reflecting the diverse roles of individual XTHs in various cell types. As there are fewer cell types in P. patens than in angiosperms such as Arabidopsis and rice, it is tempting to deduce that there are fewer XTH family genes in bryophytes. However, the present study unexpectedly identified as many as 32 genes that potentially encode XTH family proteins in the genome of P. patens, constituting a fairly large multi‐gene family that is comparable in size with those of Arabidopsis and rice. In situ localization of xyloglucan endotransglucosylase activity in this moss indicates that some P. patens XTH proteins exhibit biochemical functions similar to those found in angiosperms, and that their expression profiles are tissue‐dependent. However, comparison of structural features of families of XTH genes between P. patens and angiosperms demonstrated the existence of several bryophyte‐specific XTH genes with distinct structural and functional features that are not found in angiosperms. These bryophyte‐specific XTH genes might have evolved to meet morphological and functional needs specific to the bryophyte. These findings raise interesting questions about the biological implications of the XTH family of proteins in non‐seed plants. 相似文献
963.
Kazuhiko Aoyagi Johannes M Dijkstra Chun Xia Ikuo Denda Mitsuru Ototake Keiichiro Hashimoto Teruyuki Nakanishi 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(1):260-273
The classical MHC class I genes have been known to be highly polymorphic in various vertebrates. To date, putative allelic sequences of the classical MHC class I genes in teleost fish have been reported in several studies. However, the establishment of their allelic status has been hampered in most cases by the lack of appropriate genomic information. In the present study, using heterozygous and homozygous fish, we obtained classical-type MHC class I sequences of rainbow trout (Oncorhynchus mykiss) and investigated their allelic relationship by gene amplification and Southern and Northern hybridization analyses. The results indicated that all MHC class I sequences we obtained were derived from a single locus. Based on this, a unique polymorphic nature of the MHC class I locus of rainbow trout has been revealed. The mosaic combination of highly divergent ancient sequences in the peptide-binding domains is notable, and the variable nature around the boundary between the alpha3 and transmembrane domains is unprecedented. 相似文献
964.
Miyake H Komura M Itoh S Kosugi M Kashino Y Satoh K Shibata Y 《Photosynthesis research》2011,110(1):39-48
A time-resolved fluorescence study of living lichen thalli at 5 K was conducted to clarify the dynamics and mechanism of the
effective dissipation of excess light energy taking place in lichen under extreme drought conditions. The decay-associated
spectra obtained from the experiment at 5 K were characterized by a drastically sharpened spectral band which could not be
resolved by experiments at higher temperatures. The present results indicated the existence of two distinct dissipation components
of excess light energy in desiccated lichen; one is characterized as rapid fluorescence decay with a time constant of 27 ps
in the far-red region that was absent in wet lichen thalli, and the other is recognized as accelerated fluorescence decay
in the 685–700 nm spectral region. The former energy-dissipation component with extremely high quenching efficiency is most
probably ascribed to the emergence of a rapid quenching state in the peripheral-antenna system of photosystem II (PS II) on
desiccation. This is an extremely effective protection mechanism of PS II under desiccation, which lichens have developed
to survive in the severely desiccated environments. The latter, which is less efficient at 5 K, might have a supplementary
role and take place either in the core antenna of PS II or aggregated peripheral antenna of PS II. 相似文献
965.
966.
Soejima K Yuguchi M Mizuguchi J Tomokiyo K Nakashima T Nakagaki T Iwanaga S 《The Journal of biological chemistry》2002,277(50):49027-49035
To elucidate the functions of the surface loops of VIIa, we prepared two mutants, VII-30 and VII-39. The VII-30 mutant had all of the residues in the 99 loop replaced with those of trypsin. In the VII-39 mutant, both the 99 and 170 loops were replaced with those of trypsin. The k(cat)/K(m) value for hydrolysis of the chromogenic peptidyl substrate S-2288 by VIIa-30 (103 mm(-)1s(-)1) was 3-fold higher than that of wild-type VIIa (30.3 mm(-)1 s(-)1) in the presence of soluble tissue factor (sTF). This enhancement was due to a decrease in the K(m) value but not to an increase in the k(cat) value. On the other hand, the k(cat)/K(m) value for S-2288 hydrolysis by VIIa-39 (17.9 mm(-)1 s(-)1) was 18-fold higher than that of wild-type (1.0 mm(-)1 s(-)1) in the absence of sTF, and the value was almost the same as that of wild-type measured in the presence of sTF. This enhancement was due to not only a decrease in the K(m) value but also to an increase in the k(cat) value. These results were in good agreement with their susceptibilities to a subsite 1-directed serine protease inhibitor. In our previous paper (Soejima, K., Mizuguchi, J., Yuguchi, M., Nakagaki, T., Higashi, S., and Iwanaga, S. (2001) J. Biol. Chem. 276, 17229-17235), the replacement of the 170 loop of VIIa with that of trypsin induced a 10-fold enhancement of the k(cat) value for S-2288 hydrolysis as compared with that of wild-type VIIa in the absence of sTF. These results suggested that the 99 and the 170 loop structures of VIIa independently affect the K(m) and k(cat) values, respectively. Furthermore, we studied the effect of mutations on proteolytic activity toward S-alkylated lysozyme as a macromolecular substrate and the activation of natural macromolecular substrate factor X. 相似文献
967.
The correlation between the ATP-dependent Ca2+ binding and the phosphorylation of the membranes from swine and bovine erythrocytes was studied. The Ca2+ binding was measured by using 45CaCl2, and the phosphorylation by [γ-32P]ATP was studied with the technique of SDS polyacrylamide gel electrophoresis. 200 mM NaCl and KCl markedly repressed the Ca2+ binding of swine erythrocyte membranes. The radioactivity of 32P-labelled membranes was revealed mainly in 250 000 dalton protein and a lipid fraction. NaCl and KCl also repressed the phosphorylation of the lipid which was identified as triphosphoinositide by paper chromatography. The membranes prepared from trypsin-digested erythrocytes completely retained the Ca2+-binding activity, and lost 30% of activity. The Ca2+-binding and ATPase activity of isolated membranes decreased to 55% and to 0%, respectively, by tryptic digestion. Neither the Ca2+ binding nor the phosphorylation of polyphosphoinositides were detected in bovine erythrocyte membranes.These results suggest that the formation of triphosphoinositide rather than the of membranes is linked to the ATP-dependent Ca2+ binding of erythrocyte membranes. 相似文献
968.
969.
End-stage renal disease (ESRD) with and/or without treatment by hemodialysis (HD) is associated with accelerated atherosclerosis,
leading to cardiovascular disease (CVD) including acute coronary syndromes. Therefore, the regulation of CVD is a crucial
issue for ESRD patients. Given the recent reports that paraoxonase-1 (PON-1) and ischemia-modified albumin (IMA) could predict
CVD-related mortality in ESRD, the two recent biomarkers may be useful for preventive strategies for CVD. This review paper
presents current data on the relationships between PON-1, IMA, and ESRD. Many studies have shown that circulating PON-1 activity
is lower in ESRD patients, and we have shown that its levels increase after HD. Although circulating IMA levels can increase
before HD in ESRD patients, there remains to be little data. Our pilot study has shown a significant inverse correlation between
PON-1 and IMA in ESRD patients. Although the pathogenic link between PON-1 and IMA remains speculative, considering both biomarkers
may provide new insights into the prevention of CVD in ESRD patients. 相似文献
970.
Okugawa S Yanagimoto S Tsukada K Kitazawa T Koike K Kimura S Nagase H Hirai K Ota Y 《Cellular microbiology》2006,8(10):1571-1580
Flagellin, the structural component of bacterial flagella, is secreted by pathogenic and commensal bacteria, and is recognized by Toll-like receptor (TLR) 5. Flagellin is a common bacterial antigen present on most motile bacteria and is speculated to contribute to the activation of CD4+ T cells in the intestine. However, molecular mechanisms by which flagellin regulate T cell activation remains to be determined. Using Jurkat T cells or human primary T cell, we showed that flagellin stimulation induced tyrosine phosphorylation of TLR5 and activation of both mitogen-activated protein kinases and nuclear factor kappaB. In addition, stimulation by flagellin did not induce nuclear factor of activated T cells (NFAT) activation, while stimulation via the T cell receptor (TCR) leads to activation of NFAT. However, TCR-mediated NFAT activation and tyrosine phosphorylation of zeta-associated protein 70 (Zap-70) were inhibited in cells pre-stimulated by flagellin. Furthermore, flagellin stimulation induced suppressor of cytokine signalling-1 (SOCS-1), which formed a complex with Zap-70 after stimulation via TCR, and inhibition of SOCS-1 expression by SOCS-1-specific small interfering RNA reinstated TCR-mediated activation of NFAT in cells pre-stimulated with flagellin. These results collectively indicate that bacterial flagellin inhibits TCR-mediated activation of T cells by inducing SOCS-1. 相似文献