275 resultados para peptidyl proly isomerase


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dispersal is a highly important life history trait. In fragmented landscapes the long-term persistence of populations depends on dispersal. Evolution of dispersal is affected by costs and benefits and these may differ between different landscapes. This results in differences in the strength and direction of natural selection on dispersal in fragmented landscapes. Dispersal has been shown to be a nonrandom process that is associated with traits such as flight ability in insects. This thesis examines genetic and physiological traits affecting dispersal in the Glanville fritillary butterfly (Melitaea cinxia). Flight metabolic rate is a repeatable trait representing flight ability. Unlike in many vertebrates, resting metabolic rate cannot be used as a surrogate of maximum metabolic rate as no strong correlation between the two was found in the Glanville fritillary. Resting and flight metabolic rate are affected by environmental variables, most notably temperature. However, only flight metabolic rate has a strong genetic component. Molecular variation in the much-studied candidate locus phosphoglucose isomerase (Pgi), which encodes the glycolytic enzyme PGI, has an effect on carbohydrate metabolism in flight. This effect is temperature dependent: in low to moderate temperatures individuals with the heterozygous genotype at the single nucleotide polymorphism (SNP) AA111 have higher flight metabolic rate than the common homozygous genotype. At high temperatures the situation is reversed. This finding suggests that variation in enzyme properties is indeed translated to organismal performance. High-resolution data on individual female Glanville fritillaries moving freely in the field were recorded using harmonic radar. There was a strong positive correlation between flight metabolic rate and dispersal rate. Flight metabolic rate explained one third of the observed variation in the one-hour movement distance. A fine-scaled analysis of mobility showed that mobility peaked at intermediate ambient temperatures but the two common Pgi genotypes differed in their reaction norms to temperature. As with flight metabolic rate, heterozygotes at SNP AA111 were the most active genotype in low to moderate temperatures. The results show that molecular variation is associated with variation in dispersal rate through the link of flight physiology under the influence of environmental conditions. The evolutionary pressures for dispersal differ between males and females. The effect of flight metabolic rate on dispersal was examined in both sexes in field and laboratory conditions. The relationship between flight metabolic rate and dispersal rate in the field and flight duration in the laboratory were found to differ between the two sexes. In females the relationship was positive, but in males the longest distances and flight durations were recorded for individuals with low flight metabolic rate. These findings may reflect male investment in mate locating. Instead of dispersing, males with high flight metabolic rate may establish territories and follow a perching strategy when locating females and hence move less on the landscape level. Males with low metabolic rate may be forced to disperse due to low competitive success or may show adaptations to an alternative strategy: patrolling. In the light of life history trade-offs and the rate of living theory having high metabolic rate may carry a cost in the form of shortened lifespan. Experiments relating flight metabolic rate to longevity showed a clear correlation in the opposite direction: high flight metabolic rate was associated with long lifespan. This suggests that individuals with high metabolic rate do not pay an extra physiological cost for their high flight capacity, rather there are positive correlations between different measures of fitness. These results highlight the importance of condition.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Bacilysin is a non-ribosomally synthesized dipeptide antibiotic that is active against a wide range of bacteria and some fungi. Synthesis of bacilysin (L-alanine-[2,3-epoxycyclohexano-4]-L-alanine) is achieved by proteins in the bac operon, also referred to as the bacABCDE (ywfBCDEF) gene cluster in B. subtilis. Extensive genetic analysis from several strains of B. subtilis suggests that the bacABC gene cluster encodes all the proteins that synthesize the epoxyhexanone ring of L-anticapsin. These data, however, were not consistent with the putative functional annotation for these proteins whereby BacA, a prephenate dehydratase along with a potential isomerase/guanylyl transferase, BacB and an oxidoreductase, BacC, could synthesize L-anticapsin. Here we demonstrate that BacA is a decarboxylase that acts on prephenate. Further, based on the biochemical characterization and the crystal structure of BacB, we show that BacB is an oxidase that catalyzes the synthesis of 2-oxo-3-(4-oxocyclohexa-2,5-dienyl)propanoic acid, a precursor to L-anticapsin. This protein is a bi-cupin, with two putative active sites each containing a bound metal ion. Additional electron density at the active site of the C-terminal domain of BacB could be interpreted as a bound phenylpyruvic acid. A significant decrease in the catalytic activity of a point variant of BacB with a mutation at the N-terminal domain suggests that the N-terminal cupin domain is involved in catalysis.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Plasmodium falciparum causes the most severe form of malaria that is fatal in many cases. Emergence of drug resistant strains of P. falciparum requires that new drug targets be-identified. This review considers in detail enzymes of the glycolytic pathway, purine salvage pathway, pyrimidine biosynthesis and proteases involved in catabolism of haemoglobin. Structural features of P. falciparum triosephosphate isomerase which could be exploited for parasite specific drug development have been highlighted. Utility of P. falciparum hypoxanthine-guanine-phosphoribosyltransferase, adenylosuccinate synthase, dihydroorotate dehydrogenase, thymidylate synthase-dihydrofolate reductase, cysteine and aspartic proteases have been elaborated in detail. The review also briefly touches upon other potential targets in P. falciparum

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The enzymes involved in the biosynthesis of isoleucine and valine have been shown to be present in cell-free extracts of Mycobacterium tuberculosis H37Rv. In addition to the known enzymes of the pathway, cell-free extracts of this organism contain a new enzyme. When cell-free extracts were incubated with acetolactate and Image -ascorbic acid, without reduced nicotinamide adenine dinucleotide phosphate, the isomer of acetolactate, viz., α-keto-β-hydroxyisovalerate, was found to accumulate and was identified by different methods. The reaction is enzymic, and Image -ascorbic acid cannot be replaced by other reducing agents such as hydroquinone, 2,6-dichlorophenol indophenol, or glutathione; by derivatives of Image -ascorbic acid such as dehydroascorbic acid or dimethyl ascorbic acid; or by cobamide coenzyme. Since the extracts also isomerize α-acetohydroxybutyrate to α-keto-β-hydroxy-β-methylvalerate, the enzyme catalyzing the reaction has been termed “acetohydroxy acid isomerase.” This is the first time that the presence of acetohydroxy acid isomerase has been reported in any biological system and that a specific metabolic role has been assigned for Image -ascorbic acid. The extract also possesses reductase activity to convert α-keto-β-hydroxyisovalerate to α,β-dihydroxyisovalerate in the presence of reduced nicotinamide adenine dinucleotide phosphate.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Acetohydroxy acid isomerase (AHA isomerase) was purified about 110-fold and separated from reductase and acetohydroxy acid isomeroreductase. The AHA isomerase was found to be homogeneous by agar and polyacrylamide gel electrophoreses at different pHs. The properties of AHA isomerase have been studied. The purified enzyme showed requirement for l-ascorbic acid and sulfate ions for its activity. Synthetic ascorbic acid sulfate could replace l-ascorbic acid and sulfate. α-Methyllactate and α-ketoisovalerate were found to inhibit AHA isomerase activity competitively whereas l-valine and l-isoleucine had no significant inhibitory effect. p-Hydroxymercuribenzoate inhibited AHA isomerase activity and the inhibition was reversed by β-mercaptoethanol.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Individuals with a particular variant of the gene phosphoglucose isomerase (Pgi ) have been shown to have superior dispersal capacity and fecundity in the Glanville fritillary butterfly (Melitaea cinxia), raising questions about the mechanisms that maintain polymorphism in this gene in the field. Here, we investigate how variation in the Pgi genotype affects female and male life history under controlled conditions. The most striking effect is the longer lifespan of genotypes with high dispersal capacity, especially in nonreproducing females. Butterflies use body reserves for somatic maintenance and reproduction, but
different resources (in thorax versus abdomen) are used under dissimilar conditions, with some interactions with the Pgi genotype. These results indicate life-history trade-offs that involve resource allocation and genotype!environment interactions, and these trade-offs are likely to contribute to the maintenance of Pgi polymorphism in the natural populations.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Formylation of the initiator tRNA is essential for normal growth of Escherichia coil, The initiator tRNA containing the U35A36 mutation (CUA anticodon) initiates from UAG codon, However, an additional mutation at position 72 (72A --> G) renders the tRNA (G72/U35A36) inactive in initiation because it is defective in formylation, In this study, we isolated U1G72/U35A36 tRNA containing a wobble base pair at 1-72 positions as an intragenic suppressor of the G72 mutation. The U1G72/U35A36 tRNA is formylated and participates in initiation. More importantly, we show that the mismatch at 1-72 positions of the initiator tRNA, which was thus far thought to be the hallmark of the resistance of this tRNA against peptidyl-tRNA hydrolase (PTH), is not sufficient, The amino acid attached to the initiator tRNA is also important in conferring protection against PTH. Further, we show that the relative levels of PTH and IF2 influence the path adopted by the initiator tRNAs in protein synthesis. These findings provide an important clue to understand the dual function of the single tRNA(Met) in initiation and elongation, in the mitochondria of various organisms.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The enzymatic pathway for the synthesis of sn-glycerol 3-phosphate was investigated in developing groundnut seeds (Arachis hypogaea). Glycerol-3-phosphate dehydrogenase was not detected in this tissue but an active glycerokinase was demonstrated in the cytosolic fraction. It showed an optimum pH at 8.6 and positive cooperative interactions with both glycerol and ATP. Triosephosphate isomerase and glyceraldehyde-3-phosphate phosphatase were observed mainly in the cytosolic fraction while an active glyceraldehyde reductase was found mainly in the mitochondrial and microsomal fractions. The glyceraldehyde 3-phosphate phosphatase showed specificity and positive cooperativity with respect to glyceraldehyde 3-phosphate. The glyceraldehyde reductase was active toward glucose and fructose but not toward formaldehyde and showed absolute specificity toward NADPH. It is concluded that in the developing groundnut seed, sn-glycerol 3-phosphate is synthesized essentially by the pathway dihydroxyacetone phosphate ? glyceraldehyde 3-phosphate ?Pi glyceraldehyde ?NADPH glycerol ?ATP glycerol 3-phosphate. All the enyzmes of this pathway showed activity profiles commensurate with their participation in triacylglycerol synthesis which is maximal during the period 15�35 days after fertilization. Glycerokinase appears to be the rate-limiting enzyme in this pathway.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Moonlighting functions have been described for several proteins previously thought to localize exclusively in the cytoplasm of bacterial or eukaryotic cells. Moonlighting proteins usually perform conserved functions, e. g. in glycolysis or as chaperonins, and their traditional and moonlighting function(s) usually localize to different cell compartments. The most characterized moonlighting proteins in Grampositive bacteria are the glycolytic enzymes enolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which function in bacteria-host interactions, e. g. as adhesins or plasminogen receptors. Research on bacterial moonlighting proteins has focused on Gram-positive bacterial pathogens, where many of their functions have been associated with bacterial virulence. In this thesis work I show that also species of the genus Lactobacillus have moonlighting proteins that carry out functions earlier associated with bacterial virulence only. I identified enolase, GAPDH, glutamine synthetase (GS), and glucose-6-phosphate isomerase (GPI) as moonlighting proteins of Lactobacillus crispatus strain ST1 and demonstrated that they are associated with cell surface and easily released from the cell surface into incubation buffer. I also showed that these lactobacillar proteins moonlight either as adhesins with affinity for basement membrane and extracellular matrix proteins or as plasminogen receptors. The mechanisms of surface translocation and anchoring of bacterial moonlighting proteins have remained enigmatic. In this work, the surface localization of enolase, GAPDH, GS and GPI was shown to depend on environmental factors. The members of the genus Lactobacillus are fermentative organisms that lower the ambient pH by producing lactic acid. At acidic pH enolase, GAPDH, GS and GPI were associated with the cell surface, whereas at neutral pH they were released into the buffer. The release did not involve de novo protein synthesis. I showed that purified recombinant His6-enolase, His6-GAPDH, His6-GS and His6-GPI reassociate with cell wall and bind in vitro to lipoteichoic acids at acidic pH. The in-vitro binding of these proteins localizes to cell division septa and cell poles. I also show that the release of moonlighting proteins is enhanced in the presence of cathelicidin LL- 37, which is an antimicrobial peptide and a central part of the innate immunity defence. I found that the LL-37-induced detachment of moonlighting proteins from cell surface is associated with cell wall permeabilization by LL-37. The results in this thesis work are compatible with the hypothesis that the moonlighting proteins of L. crispatus associate to the cell wall via electrostatic or ionic interactions and that they are released into surroundings in stress conditions. Their surface translocation is, at least in part, a result from their release from dead or permeabilized cells and subsequent reassociation onto the cell wall. The results of this thesis show that lactobacillar cells rapidly change their surface architecture in response to environmental factors and that these changes influence bacterial interactions with the host.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A phylogenetic or evolutionary tree is constructed from a set of species or DNA sequences and depicts the relatedness between the sequences. Predictions of future sequences in a phylogenetic tree are important for a variety of applications including drug discovery, pharmaceutical research and disease control. In this work, we predict future DNA sequences in a phylogenetic tree using cellular automata. Cellular automata are used for modeling neighbor-dependent mutations from an ancestor to a progeny in a branch of the phylogenetic tree. Since the number of possible ways of transformations from an ancestor to a progeny is huge, we use computational grids and middleware techniques to explore the large number of cellular automata rules used for the mutations. We use the popular and recurring neighbor-based transitions or mutations to predict the progeny sequences in the phylogenetic tree. We performed predictions for three types of sequences, namely, triose phosphate isomerase, pyruvate kinase, and polyketide synthase sequences, by obtaining cellular automata rules on a grid consisting of 29 machines in 4 clusters located in 4 countries, and compared the predictions of the sequences using our method with predictions by random methods. We found that in all cases, our method gave about 40% better predictions than the random methods.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The discrepancy between the X-ray and NMR structures of Mycobacterium tuberculosis peptidyl-tRNA hydrolase in relation to the functionally important plasticity of the molecule led to molecular dynamics simulations. The X-ray and the NMR studies along with the simulations indicated an inverse correlation between crowding and molecular volume. A detailed comparison of proteins for which X-ray and the NMR structures appears to confirm this correlation. In consonance with the reported results of the investigations in cellular compartments and aqueous solution, the comparison indicates that the crowding results in compaction of the molecule as well as change in its shape, which could specifically involve regions of the molecule important in function. Crowding could thus influence the action of proteins through modulation of the functionally important plasticity of the molecule. Selvaraj M, Ahmad R, Varshney U and Vijayan M 2012 Crowding, molecular volume and plasticity: An assessment involving crystallography, NMR and simulations. J. Biosci. 37 953-963] DOI 10.1007/s12038-012-9276-5

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The ribosomal P-site hosts the peptidyl-tRNAs during translation elongation. Which P-site elements support these tRNA species to maintain codon-anticodon interactions has remained unclear. We investigated the effects of P-site features of methylations of G966, C967, and the conserved C-terminal tail sequence of Ser, Lys, and Arg (SKR) of the S9 ribosomal protein in maintenance of the translational reading frame of an mRNA. We generated Escherichia coli strains deleted for the SKR sequence in S9 ribosomal protein, RsmB (which methylates C967), and RsmD (which methylates G966) and used them to translate LacZ from its +1 and -1 out-of-frame constructs. We show that the S9 SKR tail prevents both the +1 and -1 frameshifts and plays a general role in holding the P-site tRNA/peptidyl-tRNA in place. In contrast, the G966 and C967 methylations did not make a direct contribution to the maintenance of the translational frame of an mRNA. However, deletion of rsmB in the S9 Delta 3 background caused significantly increased -1 frameshifting at 37 degrees C. Interestingly, the effects of the deficiency of C967 methylation were annulled when the E. coli strain was grown at 30 degrees C, supporting its context-dependent role.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

240 p. + anexos

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Cannabinoid CB1 receptors peripherally modulate energy metabolism. Here, we investigated the role of CB1 receptors in the expression of glucose/pyruvate/tricarboxylic acid (TCA) metabolism in rat abdominal muscle. Dihydrolipoamide dehydrogenase (DLD), a flavoprotein component (E3) of alpha-ketoacid dehydrogenase complexes with diaphorase activity in mitochondria, was specifically analyzed. After assessing the effectiveness of the CB1 receptor antagonist AM251 (3 mg kg(-1), 14 days) on food intake and body weight, we could identified seven key enzymes from either glycolytic pathway or TCA cycle-regulated by both diet and CB1 receptor activity-through comprehensive proteomic approaches involving two-dimensional electrophoresis and MALDI-TOF/LC-ESI trap mass spectrometry. These enzymes were glucose 6-phosphate isomerase (GPI), triosephosphate isomerase (TPI), enolase (Eno3), lactate dehydrogenase (LDHa), glyoxalase-1 (Glo1) and the mitochondrial DLD, whose expressions were modified by AM251 in hypercaloric diet-induced obesity. Specifically, AM251 blocked high-carbohydrate diet (HCD)-induced expression of GPI, TPI, Eno3 and LDHa, suggesting a down-regulation of glucose/pyruvate/lactate pathways under glucose availability. AM251 reversed the HCD-inhibited expression of Glo1 and DLD in the muscle, and the DLD and CB1 receptor expression in the mitochondrial fraction. Interestingly, we identified the presence of CB1 receptors at the membrane of striate muscle mitochondria. DLD over-expression was confirmed in muscle of CB1-/- mice. AM251 increased the pyruvate dehydrogenase and glutathione reductase activity in C2C12 myotubes, and the diaphorase/oxidative activity in the mitochondria fraction. These results indicated an up-regulation of methylglyoxal and TCA cycle activity. Findings suggest that CB1 receptors in muscle modulate glucose/pyruvate/lactate pathways and mitochondrial oxidative activity by targeting DLD.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

水母雪莲(Saussurea medusa Maxim)为名贵珍稀中药材,其主要药用成分为类黄酮,尤其是3-脱氧类黄酮。目前关于雪莲的研究主要集中在采用细胞培养生产类黄酮等方面,但对于雪莲类黄酮生物合成的分子机制了解甚少,极大限制了这一珍贵资源的利用。本研究采用水母雪莲红色系愈伤组织及悬浮细胞为材料,构建cDNA文库,从中克隆水母雪莲类黄酮次生代谢中的相关基因并对这些基因进行了深入的生物信息学分析、转基因研究初步确定其功能,以期了解雪莲类黄酮次生代谢的分子机制,为提高类黄酮的合成奠定基础。主要结果如下: 1. 成功地构建了水母雪莲红色系愈伤组织与悬浮细胞cDNA文库,原始文库滴度达到4×106pfu/ml,扩增文库滴度接近1011 pfu/ml,重组率达98%。PCR检测插入片段,均在0.5kb到3kb之间,1kb以上占62%。从文库中检测到了chs、dfr及Myb转录因子SmP,文库覆盖度达到要求且为PCR筛选文库提供了可能。 2. 采用部分简并引物,通过RT-PCR克隆了水母雪莲查尔酮异构酶基因Smchi特异探针,并根据这一探针序列设计特异引物,采用TD-PCR法筛选cDNA文库,获得Smchi cDNA序列,全长831bp,编码一个232氨基酸残基的蛋白。根据cDNA序列克隆了Smchi DNA序列,结果表明Smchi基因无内含子。Smchi cDNA序列与翠菊chi基因高度同源,ORF区域同源性高达84%,但推测氨基酸序列则只有79.3%。Smchi mRNA具有复杂的二级结构。SmCHI具有典型的Chalcone结构域,其二级结构与苜蓿CHI蛋白十分相似,7个α-螺旋与8个延伸链由随机结构联系起来。但其活性中心的第三个关键氨基酸残基N115为M115所取代,这一取代可能导致该蛋白无生物活性,也可能使它具有一般CHI不同的功能。构建Smchi正义、反义真核表达载体,通过农杆菌介导导入烟草,获得转正义、反义Smchi基因的烟草。转基因烟草花色未改变,但叶片总黄酮发生了显著的变化,50%转正义基因烟草总黄酮含量显著提高,最高比对照提高6倍,70%转反义基因烟草总黄酮含量显著下降,最多达85.1%,初步证明Smchi具有功能,并能有效调控烟草类黄酮次生代谢。因此,SmCHI可能是不同于已知CHI的一类新的CHI蛋白,它催化的反应可能与花色素合成无关,其反应机制也可能有所不同。 3. 伴随Smchi的克隆获得了一个黄烷酮3-羟化酶类似基因Smf3h的cDNA,全长1334bp,编码一个343aa的蛋白。根据这一cDNA序列克隆了Smf3h DNA序列,全长1630bp,结果表明该基因由4个外显子和3个内含子组成。Smf3h mRNA具有十分复杂的二级结构。 推测蛋白氨基酸同源性分析表明,SmF3H属于2OG-FeII_Oxy家族,与同一家族的的颠茄H6H的同源性为45%,与拟南芥F3H的同源性为40%,但对SmF3H、典型F3H及典型H6H推测蛋白二级结构、活性中心关键氨基酸残基的位置与相对距离、软件进行功能预测分析,发现SmF3H与F3H更相似。构建Smf3h的正义与反义真核表达载体,通过农杆菌介导导入烟草,但只获得一批转正义基因的烟草,反义基因导致烟草不能再生而未获得转反义基因烟草。转基因烟草花色未改变,叶片总黄酮也与对照相似,初步确认Smf3h与烟草类黄酮生物合成无关,而是一个既不属于f3h也不属于h6h的功能未确定的新基因。 4. 采用与克隆Smchi基因相似的方法,从cDNA文库中克隆了SmP基因cDNA,全长969bp,编码一个256 aa的蛋白质。根据cDNA序列克隆了SmP基因的DNA序列,结果表明,SmP基因无内含子。SmP基因cDNA 一级结构及mRNA二级结构预测分析表明,该基因A+T含量很高(63%),所形成二级结构以A-T配对为主,其稳定性可能较差。SmP推测蛋白序列具有R2R3-Myb转录因子的典型特征,在N-端具有两个Myb DNA-binding Domain,其二级结构与鸡Myb转录因子1A5J十分相似,与其他基因如水稻OsMYB、番茄ThMYB的同源区域主要集中在这一结构域,分别为71.3%和70.8%;C-端富含丝氨酸,与烟草NtMYB、葡萄VlMYB等类黄酮调控因子相似,都呈寡聚体分布,并具有相同的保守磷酸化位点S170与S206。构建SmP基因真核表达载体,通过农杆菌介导导入烟草,获得大量转基因烟草。转基因烟草花色未发生改变,但51%的转基因烟草叶片总黄酮含量都显著提高(0.5-6倍),表明SmP具有促进烟草类黄酮生物合成的功能,但所调控的支路与花色素合成无关。初步试验结果表明,转SmP基因烟草对蚜虫具有很高的抗性,可有效地抑制蚜虫在烟草上的生长,抑制率最高可达92%-100%。这一抗性与烟草中类黄酮的积累可能具有直接的联系,但还需要进一步的试验证明。 5. 与美国俄亥俄州立大学Erich Grotewold 博士实验室合作,完成了微型EST库50个克隆的测序并进行了分析,从中获得了水母雪莲花色素合酶基因SmANS及醛脱氢酶基因SmALDH的特异探针。根据SmANS特异探针设计引物,采用PCR从这50个克隆中筛选获得了SmANS的cDNA序列,全长1229bp,编码一个356aa的蛋白质。SmANS在cDNA水平上与同属的翠菊ANS基因高度同源,但同源区域集中在ORF区域,达到80%,mRNA 预测二级结构十分复杂;推测氨基酸序列与翠菊ANS同源性达到82.9%。SmANS属于2OG-FeII_Oxy家族,在2OG-FeII_Oxy结构域高度保守,与翠菊、甜橙ANS保守结构域同源性达到94%。预测蛋白二级结构以α-螺旋-β-折叠为主,由7个主螺旋和11个主β-折叠及随机结构连接而成,并具有2OG-FeII_Oxy家族活性中心的三个保守的组氨酸残基(His84、His235、His291)和一个天冬氨酸残基(Asp237)。 6. 根据微型EST库中获得的SmALDH特异探针设计引物,采用PCR从这50个克隆中筛选获得了SmALDH基因cDNA 序列,全长1664bp,编码一个491aa的蛋白质。SmALDH基因cDNA具有独特的碱基组成,3/-UTR富含A+T,占该区域碱基总量的80%,5/-UTR的A+T和G+C各占50%,比ORF区域(52%)还低,因此其mRNA二级结构中5/-UTR可以单独形成自身二级结构并且十分稳定,这可能影响基因的表达。这一现象在水稻、玉米等植物中也存在。SmALDH在cDNA水平上在ORF区域与拟南芥、藏红花、水稻等具有较高同源性,分别为64.03%、63.89%、63.72%,但在推测蛋白氨基酸序列水平上同源性反而较低,分别为54.9%、54.3%、54.0%。SmALDH缺少线粒体定位信号,为胞质醛脱氢酶,具有一个Aldedh 保守结构域,还具有与1OF7-H相似的以α-螺旋-β-折叠为主的二级结构,由10个主螺旋和15个主β-折叠及随机结构连接而成。由于ALDH在植物细胞乙醇发酵中具有解除醛类物质毒害的功能,因此SmALDH基因的克隆为改造细胞自身以适应发酵培养条件,解决水母雪莲细胞大规模培养中需氧问题提供了可能。