A mutant of Arabidopsis lacking a chloroplast-specific lipid

In order to investigate the functional significance of membrane lipid unsaturation, we have isolated a series of mutants of Arabidopsis thaliana which are deficient in particular membrane fatty acids. The first of these mutants completely lacks Delta3-trans-hexadecenoate, an acyl group that until now has been thought to play an important role in the structure or function of thylakoid membranes in photosynthetic eukaryotes. The apparent absence of any marked physiological effect of the mutation illustrates the potential of this approach to the analysis of membrane structure and function.     

Decoding in the absence of a codon by tmRNA and SmpB in the ribosome

In bacteria, ribosomes stalled at the end of truncated messages are rescued by transfer-messenger RNA (tmRNA), a bifunctional molecule that acts as both a transfer RNA (tRNA) and a messenger RNA (mRNA), and SmpB, a small protein that works in concert with tmRNA. Here, we present the crystal structure of a tmRNA fragment, SmpB and elongation factor Tu bound to the ribosome at 3.2 angstroms resolution. The structure shows how SmpB plays the role of both the anticodon loop of tRNA and portions of mRNA to facilitate decoding in the absence of an mRNA codon in the A site of the ribosome and explains why the tmRNA-SmpB system does not interfere with normal translation.     

Crystal structure of the termination module of a nonribosomal peptide synthetase

Nonribosomal peptide synthetases (NRPSs) are modular multidomain enzymes that act as an assembly line to catalyze the biosynthesis of complex natural products. The crystal structure of the 144-kilodalton Bacillus subtilis termination module SrfA-C was solved at 2.6 angstrom resolution. The adenylation and condensation domains of SrfA-C associate closely to form a catalytic platform, with their active sites on the same side of the platform. The peptidyl carrier protein domain is flexibly tethered to this platform and thus can move with its substrate-loaded 4'-phosphopantetheine arm between the active site of the adenylation domain and the donor side of the condensation domain. The SrfA-C crystal structure has implications for the rational redesign of NRPSs as a means of producing novel bioactive peptides.     

Screening and degradation characteristics of a tylosin-degrading strain

Antibiotics residues have been accumulating in the environment day by day due to overuse of antibiotics. Recalcitrant antibiotic residues, such as tylosin(TYL), can cause serious environmental problems, which makes it important to eliminate TYL from the environment. It is important to eliminate TYL from the environment. In this study, a strain was isolated and purified from fermentation by-product that came from a TYL production factory. The TYL degrading strain was identified by its morphology, physiological and biochemical reactions and sequencing the PCR-amplified fragments of its 16 S r DNAcoding genes. The temperature, shaking speed, initial TYL concentration, p H and inoculum sizes were investigated under simulated conditions by using single factor tests. The results showed that TYL2, a high efficient strain was isolated and was identified as Brevibacillus borstelensis. The degradation rate of TYL by this strain could reach to 75% with an initial concentration of 25 mg L~(–1) within 7 days under conditions of 7% B. borstelensis(v/v, 2×108 CFU m L~(–1)) at p H 7.0 and at 35°C. It is interesting that this strain has a very strong ability to degrade the TYL in natural sewage with the degradation rate of 65% within 7 days. This result could be helpful for the degradation of TYL and provide guidance for the degradation of other antibiotics.     

降解菌株P-2生物学特性及其降解性能研究

为降解土壤中农药残留,解决农副产品农药超标问题,采用富集培养法分离筛选出1株能够降解多菌灵的菌株P-2,研究初始pH、培养温度、接种量、外加碳源、氮源对其生长量和降解特性的影响。结果表明:该菌株能以多菌灵为碳源生长,在基础培养基中培养5d时对100mg.L-1的多菌灵降解率达60.6%,而另外加入氮源蛋白胨,可提高降解率达91%。降解多菌灵的适宜条件为温度25～40℃、pH 5.1～8.1,且降解率与菌体生长量呈正相关关系。     

反硝化细菌的筛选及其亚硝酸盐降解特性研究

从海水养殖池的底泥中筛选到6株反硝化细菌,其中对亚硝酸盐降解力最强的1株菌JN1初步鉴定为假单胞菌,研究了JN1的亚硝酸盐降解特性,结果表明:JN1具有高效降解转化亚硝酸钠的能力,其适宜降解条件为:亚硝酸钠浓度1 000~4 000 mg.L-1,菌种接种量5%(v/v),培养基装量100 mL(250 mL容量),中量充气发酵,发酵时间18~30 h,发酵pH值6.5~7.5。     

Photic induction of mPer1 and mPer2 in cry-deficient mice lacking a biological clock

Mice lacking mCry1 and mCry2 are behaviorally arrhythmic. As shown here, cyclic expression of the clock genes mPer1 and mPer2 (mammalian Period genes 1 and 2) in the suprachiasmatic nucleus and peripheral tissues is abolished and mPer1 and mPer2 mRNA levels are constitutively high. These findings indicate that the biological clock is eliminated in the absence of both mCRY1 and mCRY2 (mammalian cryptochromes 1 and 2) and support the idea that mammalian CRY proteins act in the negative limb of the circadian feedback loop. The mCry double-mutant mice retain the ability to have mPer1 and mPer2 expression induced by a brief light stimulus known to phase-shift the biological clock in wild-type animals. Thus, mCRY1 and mCRY2 are dispensable for light-induced phase shifting of the biological clock.     

RNA recognition and cleavage by a splicing endonuclease

The RNA splicing endonuclease cleaves two phosphodiester bonds within folded precursor RNAs during intron removal, producing the functional RNAs required for protein synthesis. Here we describe at a resolution of 2.85 angstroms the structure of a splicing endonuclease from Archaeglobus fulgidus bound with a bulge-helix-bulge RNA containing a noncleaved and a cleaved splice site. The endonuclease dimer cooperatively recognized a flipped-out bulge base and stabilizes sharply bent bulge backbones that are poised for an in-line RNA cleavage reaction. Cooperativity arises because an arginine pair from one catalytic domain sandwiches a nucleobase within the bulge cleaved by the other catalytic domain.     

钙调素mRNA在梨子房和幼果中的表达

 【目的】通过研究钙调素mRNA在梨（Pyrus pyrifolia NaKai）子房和幼果中的表达特性,探讨其在盛花后子房和幼果发育中的生理作用。【方法】以10年生黄花梨盛花前后子房和幼果为试材。Northern杂交检测钙调素基因表达水平。mRNA原位杂交进一步检测钙调素mRNA在梨子房和幼果发育过程中组织特异性表达。【结果】Northern杂交结果表明,钙调素基因在梨子房和幼果中的表达水平,花前逐渐上升,至盛花时最高,花后又下降。mRNA原位杂交结果表明,钙调素mRNA在梨果中的表达多集中于果皮、果肉、胚珠和果肉微管组织,而在果心的表达较少,且表达水平为果皮>果肉>果心,珠心>胚囊>珠被。在细胞水平上,钙调素mRNA的表达主要集中于细胞的胞间隙和胞间层及细胞核;钙调素mRNA的表达水平在各组织不同发育阶段也表现为盛花时最高,花前稍高于花后。【结论】钙调素mRNA在梨子房和幼果中大量表达,以盛花期最高,表达的部位主要集中在果皮、果肉、胚珠、维管束、细胞间隙及胞间层。钙调素mRNA在盛花期子房/幼果中的大量表达,可能与果实钙的增加有一定关系。     

间甲苯酚优势降解菌的筛选及降解性能研究

以哈尔滨某气化厂生化车间活性污泥为菌源,在不同浓度间甲苯酚的选择培养基上培养,分离筛选后进行特性研究,并利用分子鉴定的方法对菌种进行鉴定。结果表明:当间甲苯酚含量为1 000 mg.L-1,得到对间甲苯酚耐受能力最强的2个菌株,命名为JD-1和JD-2,根据间甲苯酚含量分别为300、500、600 mg.L-1的降解试验对比结果,确定JD-2菌为间甲苯酚优势降解菌。同时可知最优处理条件为:温度30℃,pH 7,葡萄糖量500 mg.L-1。通过对其菌落特征、生理生化性质以及16S rRNA测序鉴定结果得间甲苯酚优势降解菌JD-2属假单胞菌属(Pseudomonassp.)。     

Facilitation of signal onset and termination by adenylyl cyclase

The alpha subunit (Gsalpha) of the stimulatory heterotrimeric guanosine triphosphate binding protein (G protein) Gs activates all isoforms of mammalian adenylyl cyclase. Adenylyl cyclase (Type V) and its subdomains, which interact with Gsalpha, promoted inactivation of the G protein by increasing its guanosine triphosphatase (GTPase) activity. Adenylyl cyclase and its subdomains also augmented the receptor-mediated activation of heterotrimeric Gs and thereby facilitated the rapid onset of signaling. These findings demonstrate that adenylyl cyclase functions as a GTPase activating protein (GAP) for the monomeric Gsalpha and enhances the GTP/GDP exchange factor (GEF) activity of receptors.     

Sequence and expression of mRNAs encoding the alpha 1 and alpha 2 subunits of a DHP-sensitive calcium channel

Complementary DNAs were isolated and used to deduce the primary structures of the alpha 1 and alpha 2 subunits of the dihydropyridine-sensitive, voltage-dependent calcium channel from rabbit skeletal muscle. The alpha 1 subunit, which contains putative binding sites for calcium antagonists, is a hydrophobic protein with a sequence that is consistent with multiple transmembrane domains and shows structural and sequence homology with other voltage-dependent ion channels. In contrast, the alpha 2 subunit is a hydrophilic protein without homology to other known protein sequences. Nucleic acid hybridization studies suggest that the alpha 1 and alpha 2 subunit mRNAs are expressed differentially in a tissue-specific manner and that there is a family of genes encoding additional calcium channel subtypes.     

菌株BP-8的分离及其对多菌灵降解性能研究

利用增殖培养法,从长期受多菌灵污染的土壤中分离筛选出1株能够降解多菌灵的菌株BP-8,研究了pH、培养温度、接种量、外加碳源、氮源对其生长量和降解特性的影响。结果表明:该菌株能够以多菌灵为唯一碳源生长;在无机盐培养基中,5 d内对100 mg/L的多菌灵降解率为60.8%;加入0.5%的酵母粉后,对多菌灵的降解率可提高到93.2%;降解多菌灵最佳条件为30℃、pH 6.0,接种量5%,且降解率与接种量在一定范围内呈正相关。     

Movement of eukaryotic mRNAs between polysomes and cytoplasmic processing bodies

Eukaryotic cells contain nontranslating messenger RNA concentrated in P-bodies, which are sites where the mRNA can be decapped and degraded. We present evidence that mRNA molecules within yeast P-bodies can also return to translation. First, inhibiting delivery of new mRNAs to P-bodies leads to their disassembly independent of mRNA decay. Second, P-bodies decline in a translation initiation-dependent manner during stress recovery. Third, reporter mRNAs concentrate in P-bodies when translation initiation is blocked and resume translation and exit P-bodies when translation is restored. Fourth, stationary phase yeast have large P-bodies containing mRNAs that reenter translation when growth resumes. The reciprocal movement of mRNAs between polysomes and P-bodies is likely to be important in the control of mRNA translation and degradation. Moreover, the presence of related proteins in P-bodies and maternal mRNA storage granules suggests this mechanism is widely adapted for mRNA storage.     

Malathion degradation by Trichoderma viride and a Pseudomonas species

Malathion was found to be metabolized quickly by a soil fungus, Trichoderma viride, and a bacterium, Pseudomonas sp., which were originally found in soils from northern Ohio that had been sprayed heavily with insecticides. Results of a survey of the breakdown capabilities of 16 variants of T. viride revealed that certain colonies from this species had a very marked ability to breakdown malathion through the action of a carboxylesterase(s). The enzymes can be made soluble by preparing the acetone powder suspension.     

苄嘧磺隆降解菌BP-H-01的分离及降解特性

【目的】分离筛选苄嘧磺隆的高效降解菌株,为磺酰脲类除草剂土壤残留危害的综合治理提供候选生物制剂。【方法】采用查氏培养基,从采自全国5省市的23份土壤样品中筛选降解菌,以苄嘧磺隆为唯一碳源进行摇瓶培养复筛,以相对降解率为评价标准,确定高效降解菌株,根据形态初步鉴定其种属,研究其降解特性。【结果】从土壤中分离筛选出能耐受500mg/L苄嘧磺隆的真菌与细菌菌株共计78株,其中共培养2d后,菌株BP-H-01对25～500mg/L苄嘧磺隆的相对降解率达80%以上,根据形态学特征初步确定该菌株为曲霉属(Aspergillus sp.)真菌。菌株BP-H-01降解苄嘧磺隆的最适pH为7.5,最适温度为28℃,初始接菌量2g/L,在此条件下相对降解率可达84.5%。【结论】菌株BP-H-01对苄嘧磺隆具有显著降解效果。     

Pyrethroid-like biological activity of compounds lacking cyclopropane and ester groupings

The following new insecticidal compounds respond to synergism by piperonyl butoxide and block nerve excitability in the same manner as the insecticide allethrin: 1-(4-allethronyl)-acetyl-2,2-dimethyl-3-isobutenylcyclopropane (the ketone analog of allethrin) and the esters of 5-benzyl-3 furylmethanol with 2,2,3,3-tetramethylcyclopropanecarboxylic acid, 2,2,3,3-tetramethylaziridinecarboxylic acid, and N, N-diisopropylcarbamic acid. Therefore pyrethroid-like activity is not restricted to esters of cyclopropanecarboxylic acids.