Excretory/secretory chymotrypsin from Lucilia cuprina: purification, enzymatic specificity and amino acid sequence deduced from mRNA

Two chymotrypsin-like proteases were purified from the secretory and excretory material of first-instar larvae of Lucilia cuprina. The hydrolysis of N-succinyl-L-phenylalanine-nitroanilide was used to monitor the purification of these proteases which was achieved by affinity chromatography on soybean trypsin inhibitor-Sepharose followed by anion exchange and hydrophobic interaction chromatographies. The enzymatic specificity of the most abundant protease {Lucilia chymotrypsin b; LCTb) was further defined by determining the amino acid sequence of peptides released from insulin B chain after incubation with LCTb. Peptide amino acid sequences obtained from LCTb were used to design degenerate oligonucleotide primers which, in conjunction with the polymerase chain reaction, enabled cDNA coding for LCTb to be cloned and sequenced. The deduced amino acid sequence of LCTb showed many of the structural features of serine proteases as well as significant amino acid sequence homology with chymotrypsins from a diverse range of species. It is probable that LCTb plays an important role in establishing the myiasis-causing larvae of L. cuprina on host skin as well as providing nutrients for the rapidly growing larvae.     

Cloning of a family of serine protease genes from the cat flea Ctenocephalides felis

Serine protease gene fragments approximately 480 nucleotides in length were amplified from Ctenocephalides felis larval and adult cDNA libraries using degenerate oligonucleotide PCR primers. Partial clones of thirty-eight distinct serine protease encoding sequences were isolated, and nineteen different full-length cDNAs encoding mature serine proteases were subsequently cloned and sequenced. All of the mature proteases contained the histidine, aspartic acid and serine amino acids of the catalytic triad characteristic of serine proteases. The mature C. felis serine proteases had amino acid sequences that were at most 29–53% identical to those known insect and arachnid serine proteases. Two of the C. felis gene sequences had similarity with the Drosophila melanogaster developmental genes snake and stubble. mRNA expression of selected serine protease genes was examined in different life stages, tissues, genders, and in response to bloodfeeding.     

Serine proteases identified from a Costelytra zealandica (White) (Coleoptera: Scarabaeidae) midgut EST library and their expression through insect development

Costelytra zealandica larvae are pests of New Zealand pastures causing damage by feeding on the roots of grasses and clovers. The major larval protein digestive enzymes are serine proteases (SPs), which are targets for disruption in pest control. An expressed sequence tag (EST) library from healthy, third instar larval midgut tissue was constructed and analysed to determine the composition and regulation of proteases in the C. zealandica larval midgut. Gene mining identified three trypsin-like and 11 chymotrypsin-like SPs spread among four major subgroups. Representative SPs were examined by quantitative PCR and enzyme activity assayed across developmental stages. The serine protease genes examined were expressed throughout feeding stages and downregulated in nonfeeding stages. The study will improve targeting of protease inhibitors and bacterial disruptors of SP synthesis.     

The white gene of the tephritid fruit fly Bactrocera tryoni is characterized by a long untranslated 5' leader and a 12 kb first intron

A 300 bp fragment from exon 6 of the white gene of Bactrocera tryoni was used to screen a B. tryoni genomic library. One positive (∼14 kb) insert contained exons 2–6 of white by nucleotide and amino acid sequence similarity to the white genes of D. melanogaster (O'Hare et al ., 1984; Pepling & Mount, 1990). Lucilia cuprina (Garcia et al ., 1996). Ceratitis capitata (Zwiebel et al ., 1995) and Anopheles gambiae (Besansky et al ., 1995). A white 5' cDNA fragment containing exons 1, 2 and part of exon 3 was amplified, cloned and sequenced. An inverse PCR fragment of genomic DNA was generated, containing the exon 1 coding region plus ∼2.1 kb of upstream sequence, encompassing the putative promoter of the gene. Exon 1 was found to be 728 bp long, encoding the first twenty-five amino acids. The full length of intron 1 was shown to be 12 kb (amplified using long PCR protocols), up to 3 times the length of the longest white intron 1 isolated to date.     

重组Mash1慢病毒表达载体的构建

目的:克隆小鼠Mash1基因的全长cDNA,构建其慢病毒表达载体Lentivirus-Mash1,为进一步研究Mash1在神经发育及干细胞神经分化中的作用奠定基础。方法:应用RT-PCR从小鼠13d胚胎中扩增出Mash1cDNA片段,经回收纯化与pGEM-T载体连接并转化感受态细菌J M109,通过蓝白筛选、PCR扩增和双酶切鉴定出阳性菌落,并对其进行基因测序。BamHⅠ和XholⅠ双酶切pGEM-T-Mash1和Lentivirus获得的目的基因双粘片段与Lentivirus双粘线性质粒相连接,转化J M109,酶切方法鉴定重组阳性菌落。结果:PCR扩增、酶切分析及序列测定证实成功获取Mash1cDNA克隆;酶切鉴定证实Lentivirus-Mash1含有大小正确的正向Mash1cDNA片段。结论:成功建立了小鼠Mash1cDNA克隆并构建了慢病毒表达载体Lentivirus-Mash1。     

Four serine proteinases expressed in Manduca sexta haemocytes

Several putative serine proteinases were detected in Manduca sexta larval plasma by labelling with radio-active diisopropyl fluorophosphate. To begin to identify and characterize such enzymes, a polymerase chain reaction was carried out using haemocyte cDNA as template and primers designed to amplify conserved sequences from serine proteinases. Four serine proteinase cDNA fragments were cloned. These were used as probes to screen an M. sexta larval haemocyte cDNA library to obtain full-length clones encoding haemocyte proteinases 1–4 (HP1, HP2, HP3 and HP4). HP1 and HP2 contain an aminoterminal ‘clip’ domain similar to those found in horse-shoe crab clotting enzyme and clotting factor B and also in the Drosophila melanogaster proteinases snake and easter. HP3 and HP4 are most similar to proteinases from mammalian leucocytes. HP1 and HP2 are both present in plasma. HP1 is expressed in haemocytes (granular cells and oenocytoids) and not in fat body. HP2 is expressed in fat body and in granular haemocytes, plasmatocytes and oenocytoids. After injection of larvae with bacteria, the level of HP2 mRNA decreased in haemocytes and increased in fat body.     

RNA interference and dietary inhibitors induce a similar compensation response in Tribolium castaneum larvae

Tribolium castaneum is a major agriculture pest damaging stored grains and cereal products. The T. castaneum genome contains 26 cysteine peptidase genes, mostly cathepsins L and B, and seven have a major role in digestion. We targeted the expression of the most highly expressed cathepsin L gene on chromosome 10, TC011001, by RNA interference (RNAi), using double‐stranded RNA (dsRNA) constructs of different regions of the gene (3′, middle, 5′ and entire coding regions). RNA sequencing and quantitation (RNA‐seq) was used to evaluate knockdown and specificity amongst the treatments. Overall, target gene expression decreased in all treatment groups, but was more severe and specific in dsRNA targeting the 3′ and entire coding regions, encoding the proteolytic active site in the enzyme. Additional cysteine cathepsin genes also were down‐regulated (off‐target effects), but some were up‐regulated in response to RNAi treatment. Notably, some serine peptidase genes were increased in expression, especially in dsRNA targeting 5′ and middle regions, and the response was similar to the effects of dietary cysteine protease inhibitors. We manually annotated these serine peptidase genes to gain insight into function and relevance to the RNAi study. The data indicate that T. castaneum larvae compensate for the loss of digestive peptidase activity in the larval gut, regardless of the mechanism of disruption.     

Analysis of mitochondrial DNA and development of PCR-based diagnostic molecular markers for Mediterranean fruit fly (Ceratitis capitata) populations

A 2.99 kb mtDNA fragment containing two variable restriction endonuclease sites ( EcoRV and Xbal ) was subcloned and sequenced from the Mediterranean fruit fly (Ceratitis capitata). This fragment represents approximately one-fifth of the entire mitochondrial sequence. The sequence was aligned with the comparable region from Drosophila yakuba and Anopheles gambiae , resulting in 81.8% and 76.7% identity at the nucleotide level, and 77% and 67.7% identity, respectively, at the amino acid level. The sequenced region includes the complete genes for NADH dehydrogenase 4, NADH dehydrogenase 4L, NADH dehydrogenase 6, and transfer RNAs for proline, threonine and histidine, and part of the genes for NADH dehydrogenase 5 and cytochrome b. Oligonucleotide primers were designed to asymmetrically bracket each of two variable restriction endonuclease sites to allow PCR amplification and subsequent restriction endonuclease analysis of individual fly samples.     

Cloning of cDNA for proteinase 3: a serine protease, antibiotic, and autoantigen from human neutrophils

Closely similar but nonidentical NH2-terminal amino acid sequences have been reported for a protein or proteins in human neutrophils whose bioactivities is/are diverse (as a serine protease, antibiotic, and Wegener's granulomatosis autoantigen) but that share(s) several features: localization in the azurophil granules, a molecular mass of approximately 29 kD, reactivity with diisopropylfluorophosphate, and the ability to degrade elastin. We previously purified one such entity, termed p29b. Using a monospecific antibody, we have cloned from human bone marrow a cDNA encoding the complete p29b protein in its mature form, along with pre- and pro-sequences. The predicted amino acid sequence agrees closely with the NH2-terminal sequence obtained previously from purified p29b, as well as with sequences newly obtained from CNBr fragments. The primary structure is highly homologous to elastase, cathepsin G, T cell granzymes, and other serine proteases, and shares both the catalytic triad and substrate binding pocket of elastase. Hybridization of the full-length cDNA with restriction enzyme digests of human genomic DNA revealed only one fragment. This suggests that the closely related species described previously are the same, and can be subsumed by the term used for the first-described activity, proteinase 3. Proteinase 3 is more abundant in neutrophils than elastase and has a similar proteolytic profile and specific activity. Thus, proteinase 3 may share the role previously attributed to neutrophil elastase in tissue damage, and has the potential to function as an antimicrobial agent.     

Isolation and characterization of insect PC2-like prohormone convertase cDNA

Endoproteolytic processing of large precursor molecules at basic amino acid residues plays an important role in the maturation of many hormones, neuropeptides and other regulatory proteins. Enzymes performing these reactions are designated as prohormone or proprotein convertases and belong to the subtilisin family of serine proteases. The screening of a larval cDNA library of the sheep blowfly Lucilia cuprina resulted in the isolation of two cDNAs encoding a PC2-like prohormone convertase. The predicted 675 amino acid preproprotein (LcuPC2) exhibits its highest identity to invertebrate and vertebrate prohormone convertase 2 homologues, and a noticeably lower identity to the so far known insect furin-like prohormone convertases of Drosophila melanogaster and Aedes aegypti. In Northern blot experiments a signal at 2.5 kb could be detected.     

含PML/RARα（L型）与ABL双基因质粒标准品的制备及应用

目的建立一个含PML/RARα（L型）与ABL双基因质粒标准品,用于PML/RARαL型）的定量检测。方法从NB4细胞中提取总RNA并逆转录为cDNA,以此为模板,设计PML/RARα（L型）与ABL基因特异性引物进行PCR,PCR产物经琼脂糖电泳、胶回收、PCMV4载体克隆后转化DH5α工程菌,提取质粒进行酶切、测序鉴定,提取质粒用于制作荧光定量PCR标准曲线,同时对质粒的稳定性能进行评价。结果结果NB4细胞提取的总RNA完整性良好,构建的质粒经酶切鉴定后与目的条带一致,测序结果与目的片段几乎完全一致,且质粒的原始浓度为9×1012copies/ml,倍比稀释至9×104copies/ml,均能得到良好的标准曲线（R2≈1）,且质粒的稳定性好,提示含PML/RARa（L型）与ABL双基因荧光定量PCR质粒标准品构建成功。结论本研究建立了制备含PML/RARα（L型）与ABL双基因质粒标准品方法,并成功制备出稳定的含PML/RARα（L型）与ABL双基因质粒标准品。     

与人体肥胖相关的神经肽Y受体Y5基因的克隆及序列分析

目的 克隆与肥胖相关的人神经肽Y受体Y5(NPY5R)基因,并鉴定该克隆基因序列的正确性.方法 从人的脂肪组织中提取总RNA并进行反转录,以此为模板用PCR扩增NPY5R基因的cDNA,然后与pET28a+载体重组,筛选阳性克隆和DNA序列分析鉴定,测序后与CeneBank中NPY5R基因进行同源性比较和序列分析.结果 PCR扩增出-个1 300 bp左右的DNA片段,与载体重组和DNA序列分析鉴定,DNA序列分析显示克隆的DNA片段是人NPY5R基因,且所克隆的基因共编码445个氨基酸,分子量为50KD,与CeneBank中NPY5R基因序列同源性达100%.结论 克隆的人NPY5R基因与CeneBank中NPY5R序列完全一致,通过对其相关生物学信息的明确分析,为进一步应用分子生物学技术深入研究NPY5R与人体肥胖发生、发展及转化等相关作用机制及应用该基因进行其基因蛋白表达奠定了基础.