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1.
Glutamate 47 is conserved in 1-aminocyclopropane-1-carboxylate (ACC) synthases and is positioned near the sulfonium pole of (S,S)-S-adenosyl-L-methionine (SAM) in the modeled pyridoxal phosphate quinonoid complex with SAM. E47Q and E47D constructs of ACC synthase were made to investigate a putative ionic interaction between Glu47 and SAM. The k(cat)/K(m) values for the conversion of (S,S)-SAM to ACC and methylthioadenosine (MTA) are depressed 630- and 25-fold for the E47Q and E47D enzymes, respectively. The decreases in the specificity constants are due to reductions in k(cat) for both mutant enzymes, and a 5-fold increase in K(m) for the E47Q enzyme. Importantly, much smaller effects were observed for the kinetic parameters of reactions with the alternate substrates L-vinylglycine (L-VG) (deamination to form alpha-ketobutyrate and ammonia) and L-alanine (transamination to form pyruvate), which have uncharged side chains. L-VG is both a substrate and a mechanism-based inactivator of the enzyme [Feng, L., and Kirsch, J. F. (2000) Biochemistry 39, 2436-2444], but the partition ratio, k(cat)/k(inact), is unaffected by the Glu47 mutations. ACC synthase primarily catalyzes the beta,gamma-elimination of MTA from the (R,S) diastereomer of SAM to produce L-VG [Satoh, S., and Yang, S. F. (1989) Arch.Biochem. Biophys. 271, 107-112], but catalyzes the formation of ACC to a lesser extent via alpha,gamma-elimination of MTA. The partition ratios for (alpha,gamma/beta,gamma)-elimination on (R,S)-SAM are 0.4, < or =0.014, and < or =0.08 for the wild-type, E47Q, and E47D enzymes, respectively. The results of these experiments strongly support a role for Glu47 as an anchor for the sulfonium pole of (S,S)-SAM, and consequently a role as an active site determinant of reaction specificity.  相似文献   

2.
Viola muliensis Y.S. Chen & Q.E. Yang, a new species of Viola L. (Violaceae) from Sichuan, China, is described and illustrated. Viola muliensis is endemic to Muli County, south-western Sichuan. This new species has yellow flowers with very short spurs and belongs to subsection Brevicalcaratae W. Beck., section Dischidium Ging. It is distinguished from other related species by having pedatipartite leaves.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 365–368.  相似文献   

3.
Species of Cephalostachyum Munro (Poaceae: Bambusoideae) from China are distributed in Yunnan and Tibet, mainly in Yunnan. In this paper, we discussed species of Cephalostachyum and compiled a key to species from China, based on recent studies on micromorphological characters of leaf epidermis and molecular phylogenetics of paleotropical woody bamboos. There is a total of seven species of Cephalostachyum distributed in China, all in Yunnan: Cchinense (Rendle) DZ. Li et HQ. Yang, Cfuchsianum Gamble et Hook. f., Cmannii (Gamble) Stapleton et DZ. Li, Cpallidum Munro, Cpingbianense (Hsueh et YM. Yang ex Yi et al.) DZ. Li et HQ. Yang, Csanguineum (WP. Zhang) DZ. Li et HQ. Yang and Cscandens Bor. Leptocanna Chia et HL. Fung and Cvirulentum YM Yang et F. Du are synonyms of Cephalostachyum Munro and Cfuchsianum Gamble et Hook. f. respectively. On the other hand, Cpergracile Munro and Cvirgatum (Munro) Kurz are morphologically closer to Schizostachyum Nees than to Cephalostachyum, and they should be treated as members of Schizostachyum. This paper is of significance to a worldwide revision of Cephalostachyum.  相似文献   

4.
A new species of Viola (Violaceae) from north-western Yunnan, China, is described and illustrated. Viola dimorphophylla Y. S. Chen & Q. E. Yang sp. nov. is endemic to Zhongdian County, north-western Yunnan, and is very easily distinguishable from all other Chinese species of the genus by having obviously dimorphic leaves, with the basal ones being long petiolate, undivided and widely cordate, and the cauline ones sessile, linear and verticillate.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 115–119.  相似文献   

5.
IntroductionThe ostracods dealt with in the present paper were found in the Taitzehovalley in 1950 by Messrs.Y.Wang,Y.H.Lu,K.C.Yang,A.T.Mu,andJ.C.Sheng of the Institute of Palaeontology,Academia Sinica,and Messrs.S.W.Tang,C.C.Chiang and C.L.Chow of the Geological Survey ofN.E.China.The specimens were derived from the beds consisting of theyellowish green shales and thin bedded limestones at the following localitiesof Penchi district:1.Wee-Ning-Ying,east of Chien-Tun,2.Tou-Fang-Kou,west of Ying-Tze-Tun,3.Ho-Tee-Kou,4.Tien-Shih-Fu.between Sin-Ta-Pu  相似文献   

6.
李超  林云  毕海燕  云映霞 《植物研究》2018,38(3):323-329
对我国紫草科(Boraginaceae)的密花齿缘草(Eritrichium confetiflorum W. T. Wang)、锚刺果(Glochisocaryum kansuense W. T. Wang)和大花长叶微孔草(Microula trichocarpa(Maxim.) Johnst. var. macrantha W. T. Wang),唇形科(Lamiaceae)的宽叶香茶菜(Rabdosia latifolia C. Y. Wu & H. W. Li),苦苣苔科(Gesneriaceae)的矮直瓣苣苔(Ancylostemon humilis W. T. Wang)以及葫芦科(Cucurbitaceae)的黑子赤瓟(Thladiantha villosula Cogn. var. nigrita A. M. Lu & Z. Y. Zhang)原白中主模式标本引证的排印错误做了更正。密花齿缘草原白中错误地将主模式标本引证为杨昌友700422,实际应为杨昌友700442。锚刺果原白中用中文错误地将主模式标本引证为傅坤俊1989,实际应为傅坤俊1489,前者属于百合科(Liliaceae)的Asparagus sichuanicus S. C. Chen & D. Q. Liu。大花长叶微孔草原白中主模式标本引证为李馨70287,实际应为李馨72087,前者属于杜鹃花科(Ericaceae)的Rhododendron edgarianum Rehder & Wilson。宽叶香茶菜原白中主模式标本引证为曲桂龄2049,实际应为曲桂龄2046,前者属于蔷薇科(Rosaceae)的Rosa caudata Baker。矮直瓣苣苔原白中主模式标本引证为杨光辉59063,实际应为杨光辉59043,前者属于桦木科(Betulaceae)的Betula fargesii Franch.。黑子赤瓟原白中主模式标本引证为冯国楣3439,实际应为冯国楣3429,前者属于伞形科(Apiaceae)的Bupleurum rockii H. Wolff。  相似文献   

7.
对我国菊科橐吾属(Ligularia Cass.) 3种植物原白中模式标本引证的排印错误进行了改正。君范橐吾(L. lingiana S.W. Liu)原白中错误地将主模式标本引证为赵清盛82946,实际应为赵清盛、牟克平和杨亚斌8294。长毛槖吾(L. changiana S.W. Liu ex Y. L. Chen & Z. Yu Li)(=L. heterophylla C. C. Chang,为L. heterophylla Rupr.的晚出同名)主模式为蔡希陶59771,但L. heterophylla C. C. Chang 的原白中错误地将主模式标本引证为蔡希陶59711;该号标本属于唇形科的灯笼草[Clinopodium polycephalum (Vaniot) C. Y. Wu & Hsuan]。南川橐吾(L. nanchuanica S. W. Liu)原白中引证的副模式标本熊济华和周子林93871实际应为李国凤63871,前者属于桤叶树科的城口桤叶树(Clethra fargesii Franch.)。  相似文献   

8.
赵利清  杨劼 《植物研究》2006,26(3):260-260
报道了内蒙古冰草属一新变种——毛稃沙芦草(Agropyron mongolicum Keng var. helinicum L.Q.Zhao et J. Yang)。该变种外稃密被长柔毛,颖光滑无毛不同于沙芦草(A. mongolicum Keng)和毛沙芦草(A. mongolicum Keng var. villosum H.L.Ying)。  相似文献   

9.
Abstract.  A new Oriental fishfly genus, Sinochauliodes gen.n. , is described, including four species: S. fujianensis ( Yang & Yang, 1999 ) comb.n. , S. griseus ( Yang & Yang, 1999 ) comb.n. , S. maculosus sp.n. and S. squalidus sp.n. A cladistic analysis based on adult morphological characters clarified the phylogenetic status of the new genus and allowed the reconstruction of the intergeneric relationships of the subfamily Chauliodinae. Two main clades within Chauliodinae were recognized from the cladistic analysis. The Asian fishflies, together with the two Nearctic genera, Chauliodes and Nigronia , formed a monophyletic lineage, and the new genus was assigned as the sister group to the genus Parachauliodes . The biogeography of the Asian fishflies is discussed.  相似文献   

10.
采用支序分析的方法首次对古北和东洋区长足虻亚科的24属3亚属之间的系统发育关系进行了分析.结果表明,长足虻亚科为一严格的单系群,其中Ahercostomus、Allohercostomus、Tachytrechus和Aphalacrosoma为一单系群,Tachytrechus和Aphalacrosoma为姐妹群.原为寡长足虻属Hercostomus亚属之一的Gymnopternus与新属Setihercostomus的亲缘关系较近,为有效属.粗柄长足虻属Ludovicius与Sybistroma为一严格单系群,建议合并为一属.弓脉长足虻属Paraclius Coquillet应为Pelastoneurus的异名.建立3新属,即准长毛长足虻属Aphypophyllus gen nov,模式种Ahy-pophyllus sinensis(Yang,1996);准白长足虻属Aphalacrosoma gen nov,模式种Aphalacrosoma postiseta(Yang et Saigusa,2001);毛颜寡长足虻属Setihercostomus gen nov.,模式种Setihercostomus zonalis(Yang,Yang et Li,1998).原为寡长足虻属的亚属Ahercostomus提升为属,模式种Hercostomus(Ahercostomus)jiangchenganus(Yang et Saigusa,2001).建立的新组合为:Ahypophytlus sinensis(Yang,1996)comb. nov. , Aphalacrosoma hubeiense (Yang, 1998) comb. nov., A. postiseta (Yang et Saigusa, 2001) comb. nov.,A. sichuanense (Yang et Saigusa, 1999) comb. nov., Seti hercostomus setifacies (Stackelberg, 1934) comb. nov., S. zonalis (Yang, Yang et Li, 1998)comb. nov., S. wuyangensis (Wei, 1997) comb. nov., S. huangi (Zhang, Yang et Masunaga, 2004) and Ahercostomus jiangchenganus (Yanget Saigusa, 2001) comb. nov. .  相似文献   

11.
报道了陕西红门兰属(Chusua)1新变型--白花广布红门兰(Chusua nana f.alba Z.H.Wu & Q.H.Yang).新变型与原变型的区别在于:花白色,苞片和花序轴绿色;而原变型的花为紫红色或粉红色,苞片和花序轴通常为紫色.  相似文献   

12.
The primary production and the respiration of Zostera noltii beds in the Thau lagoon were studied by means of the benthic bell jar technique. Concurrently, environmental data (temperature, light and nutrients) as well as morphological data of seagrass meadows (leaf width and height, density of shoots, above/below-ground biomass ratio) were collected with the purpose of explaining most of the observed variations in metabolism. Seagrass plus epiphyte respiration rates were influenced mainly by the water temperature, showing a typical exponential response to an increase in temperature. Surprisingly, measurements of production rates were not related to incoming light intensities recorded at the seagrass canopy level. An equation frequently used for terrestrial standing crops, involving the leaf area index (LAI) and the characteristics of the canopy architecture (parameter K, depending on leaves optical and geometrical properties), was applied to the seagrass ecosystem in order to estimate the light energy actually available for the plants, i.e. the light intercepted by the seagrass canopy (Q(abs)). Linear relationships were then validated between gross production rates and calculated Q(abs) for Z. noltii beds, and the best fits were obtained with K values nearing 0.6, confirming the similarities between terrestrial graminaceae and seagrasses. A linear regression model for primary production is proposed, involving the calculated Q(abs), the water temperature and the leaf nutrient content.  相似文献   

13.
Virtual screening, a fast, computational approach to identify drug leads [Perola, E.; Xu, K.; Kollmeyer, T. M.; Kaufmann, S. H.; Prendergast, F. G. J. Med. Chem.2000, 43, 401; Miller, M. A. Nat. Rev. Drug Disc.2002, 1 220], is limited by a known challenge in crystallographically determining flexible regions of proteins. This approach has not been able to identify active inhibitors of the severe acute respiratory syndrome-associated coronavirus (SARS-CoV) using solely the crystal structures of a SARS-CoV cysteine proteinase with a flexible loop in the active site [Yang, H. T.; Yang, M. J.; Ding, Y.; Liu, Y. W.; Lou, Z. Y. Proc. Natl. Acad. Sci. U.S.A.2003, 100, 13190; Jenwitheesuk, E.; Samudrala, R. Bioorg. Med. Chem. Lett.2003, 13, 3989; Rajnarayanan, R. V.; Dakshanamurthy, S.; Pattabiraman, N. Biochem. Biophys. Res. Commun.2004, 321, 370; Du, Q.; Wang, S.; Wei, D.; Sirois, S.; Chou, K. Anal. Biochem.2005, 337, 262; Du, Q.; Wang, S.; Zhu, Y.; Wei, D.; Guo, H. Peptides2004, 25, 1857; Lee, V.; Wittayanarakul, K.; Remsungenen, T.; Parasuk, V.; Sompornpisut, P. Science (Asia)2003, 29, 181; Toney, J.; Navas-Martin, S.; Weiss, S.; Koeller, A. J. Med. Chem.2004, 47, 1079; Zhang, X. W.; Yap, Y. L. Bioorg. Med. Chem.2004, 12, 2517]. This article demonstrates a genome-to-drug-lead approach that uses terascale computing to model flexible regions of proteins, thus permitting the utilization of genetic information to identify drug leads expeditiously. A small-molecule inhibitor of SARS-CoV, exhibiting an effective concentration (EC50) of 23 microM in cell-based assays, was identified through virtual screening against a computer-predicted model of the cysteine proteinase. Screening against two crystal structures of the same proteinase failed to identify the 23-microM inhibitor. This study suggests that terascale computing can complement crystallography, broaden the scope of virtual screening, and accelerate the development of therapeutics to treat emerging infectious diseases such as SARS and Bird Flu.  相似文献   

14.
Tryparedoxin peroxidase (TXNPx), recently identified as the hydroperoxide-detoxifying enzyme of trypanosomatidae [Nogoceke, E., Gommel, D. U., Kiess, M., Kalisz, H. M. & Flohé, L. (1997) Biol. Chem. 378, 827-836], is a member of the peroxiredoxin family and is characterized by two VCP motifs. Based on a consensus sequence of TXNPx and peroxiredoxin-type peroxidases, eight TXNPx variants were designed, heterologously expressed in Escherichia coli, checked for alpha-helix content by CD and kinetically analysed. The variant Q164E was fully active, C52S, W87D and R128E were inactive and C173S, W87H, W177E and W177H showed reduced activity. Wild-type TXNPx and Q164E exhibit ping-pong kinetics with infinite maximum velocities, whereas saturation kinetics were observed with C173S and W177E. The data comply with a mechanism in which C52, primarily activated by R128 and possibly by W87, is first oxidized by hydroperoxide to a sulfenic acid derivative. C173, supported by W177, then forms an intersubunit disulfide bridge with C52. If C173 is exchanged with a redox-inactive residue (Ser) or is insufficiently activated, the redox shuttle remains restricted to C52. The shift in the kinetic pattern and decrease in specific activity of C173S and W177E may result from a limited accessibility of the oxidized C52 to tryparedoxin, which in the oxidized wild-type TXNPx presumably attacks the C173 sulfur of the disulfide bridge. The proposed mechanism of action of TXNPx is consistent with that deduced for the homologous thioredoxin peroxidase of yeast [Chae, H. Z., Uhm, T. B. & Rhee, S. G. (1994) Proc. Natl Acad. Sci. USA 91, 7022-7026] and is supported by molecular modelling based on the structure of the human peroxiredoxin 'hORF6' [Choi, H.-J., Kang, S. W. Yang, C.-H., Rhee, S. G. & Ryu, S.-E. (1998) Nat. Struct. Biol. 5, 400-406].  相似文献   

15.
Rat eosinophils contain eosinophil-associated ribonucleases (Ears) in their granules. Ears are thought to be synthesized as pre-forms and stored in the granules as mature forms. However, the N-terminal amino acid of mature Ear-1 and Ear-2 is still controversial. Therefore, we prepared two recombinant mature forms of Ear-1 and Ear-2 in which the N-terminal amino acids are Ser24 (S) [Ear-1 (S) and Ear-2 (S)] and Gln26 (Q) [Ear-1 (Q) and Ear-2 (Q)], and analyzed their biological activities by comparing them with those of pre-form Ear-1 and pre-form Ear-2. The four mature Ears showed RNase A activity as well as bovine pancreatic RNase A activity, but pre-Ear-1 and pre-Ear-2 showed no RNase A activity. Mature Ear-1 (Q) and mature Ear-2 (Q) showed more potent RNase A activity than mature Ear-1 (S) and mature Ear-2 (S), respectively. The RNase A activities of mature Ear-1 (Q) and mature Ear-2 (Q) were reduced by treatment at 96 degrees C for 20 min or with RNase inhibitor. The growth of Escherichia coli was inhibited by both pre-Ears and mature Ears in a concentration-dependent manner, and was almost completely suppressed at 1.0 microM. The bactericidal activities of mature Ear-1 (Q) and mature Ear-2 (Q) were not inhibited by RNase inhibitor, but was increased by treatment at 96 degrees C for 20 min.  相似文献   

16.
Ginet N  Lavergne J 《Biochemistry》2000,39(51):16252-16262
The apparent equilibrium constant K'(2) for electron transfer between the primary (Q(A)) and secondary (Q(B)) quinone acceptors of the reaction center was measured in chromatophores of Rhodobacter capsulatus. In the presence of the oxidized primary donor P(+), we obtained a value of K'(2)(P(+)) approximately 100 at pH 7.2, based on the rates of recombination from P(+)Q(A-) and P(+)Q(B-). K'(2) was also measured in the presence of reduced P, from the damping of semiquinone oscillations during a series of single turnover flashes. A 5-fold smaller value, K'(2)(P) approximately 20, was found. Additional information on the interactions between the donor and acceptor sides was obtained by measuring the shift of the midpoint potential of P caused by the presence of Q(B-) or Q(A-)S (where S indicates the presence of the inhibitor stigmatellin). A stabilization of the oxidized state P(+) was observed in both instances, by 10 mV for Q(B-) and 30 mV for Q(A-)S. The larger stabilization of P(+)Q(A-)S with respect to P(+)Q(B-) does not account for the effect of P(+)/P on K'(2). Analysis of these results indicates that the interactions between P(+)/P and Q(A)/Q(A)(-) are markedly modified depending on the occupancy of the Q(B) pocket by ubiquinone or by stigmatellin. We propose that the large value of K'(2)(P(+)) results essentially from a conformational destabilization of the P(+)Q(A-) state, that is relieved when the proximal site of the Q(B) pocket is occupied by stigmatellin.  相似文献   

17.
Rings of inter-helix H-bonds due to Gln at position 7, a highly conserved residue in all pore-forming peptaibols, have been suggested to play an important role in the stabilization of alamethicin channels. In an attempt to test this hypothesis, experimental studies have been undertaken on four synthetic alamethicin non-Aib analogs (Alm-dUL) in which the Gln at position 7 (Q7) is substituted by Ala, Asn, or Ser (Q7A, Q7N, or Q7S). Voltage-dependent pore formation by these analogs in planar lipid bilayers is compared at the macroscopic and single-channel conductance levels. As anticipated, the Q7A substitution abolished all channel-forming activity. The voltage dependence of macroscopic current-voltage curves was conserved with the Q7N substitution but reduced in the Q7S analog. Normalized single-channel conductance ratios between substates follow the same pattern, with the Q7S analog yielding the highest unit conductances. Channel lifetimes were the most significantly modulated parameter with markedly faster kinetics when Gln or Asn was replaced by Ser. The effect of the Q7S substitution on channel lifetimes may be explained through a reduced stabilization of bundles by inter-helix H-bonds.  相似文献   

18.
Raltegravir (MK-0518) is the first integrase (IN) inhibitor to be approved by the US FDA and is currently used in clinical treatment of viruses resistant to other antiretroviral compounds. Virological failure of Raltegravir treatment is associated with mutations in the IN gene following two main distinct genetic pathways involving either the N155 or Q148 residue. Importantly, in most cases, an additional mutation at the position G140 is associated with the Q148 pathway. Here, we investigated the viral DNA kinetics for mutants identified in Raltegravir-resistant patients. We found that (i) integration is impaired for Q148H when compared with the wild-type, G140S and G140S/Q148H mutants; and (ii) the N155H and G140S mutations confer lower levels of resistance than the Q148H mutation. We also characterized the corresponding recombinant INs properties. Enzymatic performances closely parallel ex vivo studies. The Q148H mutation ‘freezes’ IN into a catalytically inactive state. By contrast, the conformational transition converting the inactive form into an active form is rescued by the G140S/Q148H double mutation. In conclusion, the Q148H mutation is responsible for resistance to Raltegravir whereas the G140S mutation increases viral fitness in the G140S/Q148H context. Altogether, these results account for the predominance of G140S/Q148H mutants in clinical trials using Raltegravir.  相似文献   

19.
Certain phenolic compounds represent a distinct class of Photosystem (PS) II Q(B) site inhibitors. In this paper, we report a detailed study of the effects of 2,4,6-trinitrophenol (TNP) and other phenolic inhibitors, bromoxynil and dinoseb, on PS II energetics. In intact PS II, phenolic inhibitors bound to only 90-95% of Q(B) sites even at saturating concentrations. The remaining PS II reaction centers (5-10%) showed modified Q(A) to Q(B) electron transfer but were sensitive to urea/triazine inhibitors. The binding of phenolic inhibitors was 30- to 300-fold slower than the urea/triazine class of Q(B) site inhibitors, DCMU and atrazine. In the sensitive centers, the S(2)Q(A)(-) state was 10-fold less stable in the presence of phenolic inhibitors than the urea/triazine herbicides. In addition, the binding affinity of phenolic herbicides was decreased 10-fold in the S(2)Q(A)(-) state than the S(1)Q(A) state. However, removal of the oxygen-evolving complex (OEC) and associated extrinsic polypeptides by hydroxylamine (HA) washing abolished the slow binding kinetics as well as the destabilizing effects on the charge-separated state. The S(2)-multiline electron paramagnetic resonance (EPR) signal and the 'split' EPR signal, originating from the S(2)Y(Z) state showed no significant changes upon binding of phenolic inhibitors at the Q(B) site. We thus propose a working model where Q(A) redox potential is lowered by short-range conformational changes induced by phenolic inhibitor binding at the Q(B) niche. Long-range effects of HA-washing eliminate this interaction, possibly by allowing more flexibility in the Q(B) site.  相似文献   

20.
关于筇竹属和筇竹名称及命名模式的讨论   总被引:2,自引:0,他引:2  
筇竹属(Qiongzhuea Hsueh et Yi)建立于1980年,模式种基于(Q. tumidinoda Hsueh et Yi)。由于竹子是多年生植物,不是年年都开花结实,且一生只开一次花。我们当时考虑到竹子开花生物学的这种特点,以及为更方便准确鉴定该属及属以下种群,分别选用了王芳瑜、熊执权和杨开泰11563号有花、果枝标本和易同培73001号营养体标本作为(Q. tumidinoda Hsueh et Yi)的共同模式。根据《国际植物命名法规》的相关条款规定,在命名一个新种或种以下新分类群时只能是一份标本。但当时法规(Leningrad Code, Art. 7. 5. 1975; St. Louis Code, 2000 and Vienna Code, Art. 37.3. 2006)明确规定有这种情况出现时,可以从它们之中选取后选模式(Art.7.5.)。有鉴于此,我们从发表时的两号标本之中选取王芳瑜、熊执权和杨开泰11563号有花、果枝标本作为筇竹的后选模式,使筇竹和筇竹属得到合格发表。  相似文献   

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