Small nuclear ribonucleoproteins (snRNPs)are involved in trans-splicing processing of pre-mRNA in Trypanosoma cruzi. To clone T. cruzi snRNPs we screened an epimastigote cDNA library with a purified antibody raised against the Sm-binding site of a yeast sequence. A clone was obtained containing a 507 bp-insert with an ORF of 399 bp and coding for a protein of 133 amino acids. Sequence analysis revealed high identity with the L27 ribosomal proteins from different species including: Canis familiaris, Homo sapiens, Schizosaccharomyces pombe and Saccharomyces cerevisiae. This protein has not been previously described in the literature and seems to be a new ribosomal protein in T. cruzi and was given the code TcrL27. To express this recombinant T. cruzi L27 ribosomal protein in E. coli, the insert was subcloned into the pET32a vector and a 26 kDa recombinant protein was purified. Immunoblotting studies demonstrated that this purified recombinant protein was recognized by the same anti-Sm serum used in the library screening as well as by chagasic and systemic lupus erythemathosus (SLE) sera. Our results suggest that the T. cruzi L27 ribosomal protein may be involved in autoimmunity of Chagas disease.
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Medicina, 2006.; Paracoccidioides brasiliensis é um fungo termodimórfico agente causador da paracoccidioidomicosse (PCM), uma micose que afeta 10 milhões de indivíduos na América Latina. A infecção é adquirida pela inalação de propágulos aéreos produzidos pela forma miceliana do fungo, os quais se convertem à morfologia leveduriforme na temperatura do hospedeiro. P brasiliensis expressa in-vivo importantes genes que podem contribuir para a patogênese do fungo. Nós utilizamos a tecnologia do antígeno induzido in-vivo (IVIAT) para identificar novos genes de P. brasiliensis que podem ser expressos durante o processo de infecção. A técnica IVIAT é uma modificação do rastreamento imunológico que evita o uso de modelo animal e permite a identificação de antígenos expressos em vários estágios da infecção. Nós utilizamos a estratégia de IVIAT para identificar genes possivelmente induzidos in-vivo. Usando esta técnica nós selecionamos proteínas imunogênicas que poderiam ser expressas especificamente durante a infecção e não durante o crescimento sob condições padrões do laboratório. O soro de onze pacientes com PCM obtidos em Goiânia...
Considering the scarcity of defined antigens, actually useful and reliable for use in the field studies, we propose an alternative method for selection of cDNA clones with potential use in the diagnosis of schistosomiasis. Human antibodies specific to a protein fraction of 31/32 kDa (Sm31/32), dissociated from immune complexes, are used for screening of clones from an adult worm cDNA library. Partial sequencing of five clones, selected through this strategy, showed to be related to Schistosoma mansoni: two were identified as homologous to heat shock protein 70, one to glutathione S-transferase, one to homeodomain protein, and one to a previously described EST (expressed sequence tag) of S. mansoni. This last clone was the most consistently reactive during the screening process with the anti-Sm31/32 antibodies dissociated from the immune complexes. The complete sequence of this clone was obtained and the translation data yielded only one ORF (open reading frame) that code for a protein with 57 amino acids. Based on this amino acid sequence two peptides were chemically synthesized and evaluated separately against a pool of serum samples from schistosomiasis patients and non-schistosomiasis individuals. Both peptides showed strong reactivity only against the positive pool...
A total of 880 expressed sequence tags (EST) originated from clones randomly selected from a Trypanosoma cruzi amastigote cDNA library have been analyzed. Of these, 40% (355 ESTs) have been identified by similarity to sequences in public databases and classified according to functional categorization of their putative products. About 11% of the mRNAs expressed in amastigotes are related to the translational machinery, and a large number of them (9% of the total number of clones in the library) encode ribosomal proteins. A comparative analysis with a previous study, where clones from the same library were selected using sera from patients with Chagas disease, revealed that ribosomal proteins also represent the largest class of antigen coding genes expressed in amastigotes (54% of all immunoselected clones). However, although more than thirty classes of ribosomal proteins were identified by EST analysis, the results of the immunoscreening indicated that only a particular subset of them contains major antigenic determinants recognized by antibodies from Chagas disease patients.
Zeatin is the most active and ubiquitous of the naturally occurring cytokinins. The O-glucoside of zeatin, found in all plants examined, is considered to be important in cytokinin transport, storage, and protection against cytokinin oxidases. The enzyme UDPglucose:zeatin O-glucosyltransferase (EC 220.127.116.11) was previously isolated from Phaseolus lunatus seeds. Immunoscreening of an expression library with monospecific antibody resulted in the isolation of a cDNA encoding the enzyme. The recombinant protein efficiently converts labeled zeatin to O-glucosylzeatin and has properties similar to the native enzyme. The cDNA of 1.5 kb contains an ORF encoding a 51.4-kDa polypeptide of 459 amino acids. The sequence is unique based on a blast search of data bases. The genomic sequence, isolated with PCR using specific primers based on the cDNA sequence, does not contain introns. The cloning of this gene provides the tools for further study of the regulation of cytokinin metabolism and analysis of the precise role of O-glucosylzeatin in plant development.
The signal sequence trap method was used to isolate cDNAs
corresponding to proteins containing secretory leader peptides and
whose genes are expressed specifically in the salivary glands of the
malaria vector Anopheles gambiae. Fifteen unique cDNA
fragments, ranging in size from 150 to 550 bp, were isolated and
sequenced in a first round of immunoscreening in COS-7 cells. All but
one of the cDNAs contained putative signal sequences at their 5′ ends,
suggesting that they were likely to encode secreted or transmembrane
proteins. Expression analysis by reverse transcription–PCR showed that
at least six cDNA fragments were expressed specifically in the salivary
glands. Fragments showing a high degree of similarity to D7 and
apyrase, two salivary gland-specific genes previously found in
Aedes aegypti, were identified. Of interest, three
different D7-related cDNAs that are likely to represent a new gene
family were found in An. gambiae. Moreover, three salivary
gland-specific cDNA fragments that do not show similarity to known
proteins in the databases were identified, and the corresponding full
length cDNAs were cloned and sequenced. RNA in situ
hybridization to whole female salivary glands showed patterns of
expression that overlap only in part those observed in the culicine
mosquito A. aegypti.
Peroxisomes in human liver contain two distinct acyl-CoA
oxidases with different substrate specificities: (i)
palmitoyl-CoA oxidase, oxidizing very long straight-chain fatty acids
and eicosanoids, and (ii) a branched-chain acyl-CoA
oxidase (hBRCACox), involved in the degradation of long branched fatty
acids and bile acid intermediates. The accumulation of branched fatty
acids and bile acid intermediates leads to severe mental retardation
and death of the diseased children. In this study, we report the
molecular characterization of the hBRCACox, a prerequisite for studying
mutations in patients with a single enzyme deficiency. The composite
cDNA sequence of hBRCACox, derived from overlapping clones isolated via
immunoscreening and hybridization of human liver cDNA expression
libraries, consisted of 2225 bases and contained an open reading frame
of 2046 bases, encoding a protein of 681 amino acids with a calculated
molecular mass of 76,739 Da. The C-terminal tripeptide of the protein
is SKL, a known peroxisome targeting signal. Sequence comparison with
the other acyl-CoA oxidases and evolutionary analysis revealed that,
despite its broader substrate specificity, the hBRCACox is the human
homolog of rat trihydroxycoprostanoyl-CoA oxidase (rTHCCox) and that
separate gene duplication events led to the occurrence in mammals of
acyl-CoA oxidases with different substrate specificities. Northern blot
analysis demonstrated that—in contrast to the rTHCCox gene—the
hBRCACox gene is transcribed also in extrahepatic tissues such as
Ovarian carcinomas are thought to arise from cells of the ovarian
surface epithelium by mechanisms that are poorly understood. Molecules
associated with neoplasia are potentially immunogenic, but few ovarian
tumor antigens have been identified. Because ovarian carcinomas can
elicit humoral responses in patients, we searched for novel tumor
antigens by immunoscreening a cDNA expression library with ovarian
cancer patient serum. Seven clones corresponding to the homeobox gene
HOXB7 were isolated. ELISAs using purified recombinant
HOXB7 protein revealed significant serologic reactivity to HOXB7 in 13
of 39 ovarian cancer patients and in only one of 29 healthy women
(P < 0.0001). Ovarian carcinomas were found to
express HOXB7 at markedly higher levels than normal
ovarian surface epithelium, suggesting that immunogenicity of HOXB7 in
patients could be associated with its elevated expression in ovarian
carcinomas. Overexpression of HOXB7 in immortalized
normal ovarian surface epithelial cells dramatically enhanced cellular
proliferation. Furthermore, HOXB7 overexpression
increased intracellular accumulation and secretion of basic fibroblast
growth factor, a potent angiogenic and mitogenic factor. These results
reveal HOXB7 as a tumor antigen whose up-regulated expression could
play a significant role in promoting growth and development of ovarian
This report demonstrates that the investigational prostatic carcinoma marker known as the prostate-specific membrane antigen (PSM) possesses hydrolytic activity with the substrate and pharmacologic properties of the N-acetylated alpha-linked acidic dipeptidase (NAALADase). NAALADase is a membrane hydrolase that has been characterized in the mammalian nervous system on the basis of its catabolism of the neuropeptide N-acetylaspartylglutamate (NAAG) to yield glutamate and N-acetylaspartate and that has been hypothesized to influence glutamatergic signaling processes. The immunoscreening of a rat brain cDNA expression library with anti-NAALADase antisera identified a 1428-base partial cDNA that shares 86% sequence identity with 1428 bases of the human PSM cDNA [Israeli, R. S., Powell, C. T., Fair, W. R. & Heston, W.D.W. (1993) Cancer Res. 53, 227-230]. A cDNA containing the entire PSM open reading frame was subsequently isolated by reverse transcription-PCR from the PSM-positive prostate carcinoma cell line LNCaP. Transient transfection of this cDNA into two NAALADase-negative cell lines conferred NAAG-hydrolyzing activity that was inhibited by the NAALADase inhibitors quisqualic acid and beta-NAAG. Thus we demonstrate a PSM-encoded function and identify a NAALADase-encoding cDNA. Northern analyses identify at least six transcripts that are variably expressed in NAALADase-positive but not in NAALADase-negative rat tissues and human cell lines; therefore...
The biosynthesis of gibberellins (GAs) after GA12-aldehyde involves a series of oxidative steps that lead to the formation of bioactive GAs. Previously, a cDNA clone encoding a GA 20-oxidase [gibberellin, 2-oxoglutarate:oxygen oxidoreductase (20-hydroxylating, oxidizing), EC 1.14.11.-] was isolated by immunoscreening a cDNA library from liquid endosperm of pumpkin (Cucurbita maxima L.) with antibodies against partially purified GA 20-oxidase. Here, we report isolation of a genomic clone for GA 20-oxidase from a genomic library of the long-day species Arabidopsis thaliana Heynh., strain Columbia, by using the pumpkin cDNA clone as a heterologous probe. This genomic clone contains a GA 20-oxidase gene that consists of three exons and two introns. The three exons are 1131-bp long and encode 377 amino acid residues. A cDNA clone corresponding to the putative GA 20-oxidase genomic sequence was constructed with the reverse transcription-PCR method, and the identity of the cDNA clone was confirmed by analyzing the capability of the fusion protein expressed in Escherichia coli to convert GA53 to GA44 and GA19 to GA20. The Arabidopsis GA 20-oxidase shares 55% identity and > 80% similarity with the pumpkin GA 20-oxidase at the derived amino acid level. Both GA 20-oxidases share high homology with other 2-oxoglutarate-dependent dioxygenases (2-ODDs)...
A phage display approach was utilized to modify the specificity of each of the three fingers of the murine transcription factor Zif268. Selections were performed by using the consensus binding sequence of the natural protein and a conserved sequence in the genome of the type 1 human immunodeficiency virus. By using an extensive randomization strategy, the entire 3-bp specificity of a finger has been changed. Rapid analysis of selected zinc fingers was facilitated by the development of an immunoscreening assay for DNA binding and specificity. To investigate the mechanism of binding and specificity, the binding kinetics of Zif268 and 10 selected variants were determined in real time with an assay based on surface plasmon resonance. Differential mechanisms for sequence-specific recognition were observed. No evidence in support of a single general coding relationship between zinc finger and target DNA sequence was observed. The prospects for the development of this class of proteins in human therapy are considered.
A cDNA clone encoding the major intestinal cytosolic 14-kDa bile acid-binding protein (14-kDa I-BABP) was isolated from a rat ileal lambda gt22A library following immunoscreening using a monospecific antiserum raised against a 14-kDa polypeptide found in the rat ileal cytosol. One clone of 516 bp encoded a 128-amino acid protein with a predicted molecular mass of 14,544 Da. The deduced amino acid sequence of 14-kDa I-BABP showed 100% homology to rat intestinal 15-kDa protein (I-15P) and 72% homology to porcine 15-kDa gastrotropin, whereas comparison of I-BABP to rat 14-kDa fatty acid-binding proteins of liver, intestine, and heart revealed homologies of 44%, 25%, and 28%, respectively. Northern blot analysis revealed a single transcript of approximately 0.5 kb in ileum and ovary; however, the abundance of I-BABP mRNA was much greater in ileum than in ovary. No transcript was seen in RNA extracted from stomach, jejunum, colon, liver, adrenal, brain, heart, kidney, or testis. Transfection of the I-BABP cDNA into COS-7 cells resulted in the expression of a 14-kDa protein that was identical to the ileal cytosolic I-BABP as determined by immunoblotting. Photoaffinity labeling of expressed 14-kDa protein was saturable with respect to increasing concentrations of 7...
The tropane alkaloid scopolamine is a medicinally important anticholinergic drug present in several solanaceous plants. Hyoscyamine 6 beta-hydroxylase (EC 18.104.22.168) catalyzes the oxidative reactions in the biosynthetic pathway leading from hyoscyamine to scopolamine. We introduced the hydroxylase gene from Hyoscyamus niger under the control of the cauliflower mosaic virus 35S promoter into hyoscyamine-rich Atropa belladonna by the use of an Agrobacterium-mediated transformation system. A transgenic plant that constitutively and strongly expressed the transgene was selected, first by screening for kanamycin resistance and then by immunoscreening leaf samples with an antibody specific for the hydroxylase. In the primary transformant and its selfed progeny that inherited the transgene, the alkaloid contents of the leaf and stem were almost exclusively scopolamine. Such metabolically engineered plants should prove useful as breeding materials for obtaining improved medicinal components.
Recent evidence indicates that the commitment to degrade cellular proteins by the ubiquitin proteolytic pathway is dependent on the covalent attachment of multiubiquitin chains to the target protein [Chau, V., Tobias, J. W., Bachmair, A., Marriott, D., Ecker, D. J., Gonda, D. K. & Varshavsky, A. (1989) Science 243, 1576-1583]. We have isolated a 20-kDa ubiquitin carrier protein [E2(20 kDa)] from wheat by using ubiquitin covalent affinity chromatography and anion-exchange HPLC that catalyzes multiubiquitin chain formation in vitro. This reaction is blocked by the addition of a mutant ubiquitin in which arginine has been substituted for lysine at residue 48, demonstrating that the coupling of ubiquitin to ubiquitin is likely to be through an isopeptide linkage between the C-terminal glycine and Lys48 of ubiquitin. By immunoscreening a wheat cDNA expression library with anti-E2(20 kDa) antibodies, a cDNA encoding the complete protein was isolated. The clone (designated UBC7) was confirmed as encoding E2(20 kDa) by comparison of the derived amino acid sequence with peptide sequences of E2(20 kDa) tryptic fragments. The encoded protein contains a single cysteine at position 91, which is presumably the active site, and has regions of amino acid sequence similarity to other known E2s from plants and yeast. Expression of this cDNA in Escherichia coli produced an active E2 capable of catalyzing multiubiquitin chain formation in vitro. By virtue of its activity...
Protein 4.2 (P4.2) comprises approximately 5% of the protein mass of human erythrocyte (RBC) membranes. Anemia occurs in patients with RBCs deficient in P4.2, suggesting a role for this protein in maintaining RBC stability and integrity. We now report the molecular cloning and characterization of human RBC P4.2 cDNAs. By immunoscreening a human reticulocyte cDNA library and by using the polymerase chain reaction, two cDNA sequences of 2.4 and 2.5 kilobases (kb) were obtained. These cDNAs differ only by a 90-base-pair insert in the longer isoform located three codons downstream from the putative initiation site. The 2.4- and 2.5-kb cDNAs predict proteins of approximately 77 and approximately 80 kDa, respectively, and the authenticity was confirmed by sequence identity with 46 amino acids of three cyanogen bromide-cleaved peptides of P4.2. Northern blot analysis detected a major 2.4-kb RNA species in reticulocytes. Isolation of two P4.2 cDNAs implies existence of specific regulation of P4.2 expression in human RBCs. Human RBC P4.2 has significant homology with human factor XIII subunit a and guinea pig liver transglutaminase. Sequence alignment of P4.2 with these two transglutaminases, however, revealed that P4.2 lacks the critical cysteine residue required for the enzymatic crosslinking of substrates.
Human babesiosis in the United States is caused predominantly by Babesia microti, a tick-transmitted blood parasite. Improved testing methods for the detection of infection with this parasite are needed, since asymptomatic B. microti infection represents a potential threat to the blood supply in areas where B. microti is endemic. We performed immunoscreening of an expression library of genomic DNA from a human isolate of B. microti (strain MN1). Among 17 unique immunoreactive clones, we identified 9 which represent a related family of genes with little sequence homology to other known sequences but with an architecture resembling that of several surface proteins of Plasmodium. Within this family, a tandem array of a degenerate six-amino-acid repeat (SEAGGP, SEAGWP, SGTGWP, SGTVGP) was found in various lengths between relatively well conserved segments at the N and C termini. In order to examine within-clone variation, we developed a PCR protocol for direct recovery of a specific bmn1-6 homologue directly from 30 human blood isolates, 4 corresponding hamster isolates, and 5 geographically corresponding Peromyscus leucopus (white-footed mouse) isolates. Isolates from the hamsters had the same sequences as those found in the corresponding human blood...
The search for appropriate vaccine candidates and drug targets against onchocerciasis has so far been confronted with several limitations due to the unavailability of biological material, appropriate molecular resources, and knowledge of the parasite biology. To identify targets for vaccine or chemotherapy development we have undertaken two approaches. First, cDNA expression libraries were constructed from life cycle stages that are critical for establishment of Onchocerca volvulus infection, the third-stage larvae (L3) and the molting L3. A gene discovery effort was then initiated by random expressed sequence tag analysis of 5,506 cDNA clones. Cluster analyses showed that many of the transcripts were up-regulated and/or stage specific in either one or both of the cDNA libraries when compared to the microfilariae, L2, and both adult stages of the parasite. Homology searches against the GenBank database facilitated the identification of several genes of interest, such as proteinases, proteinase inhibitors, antioxidant or detoxification enzymes, and neurotransmitter receptors, as well as structural and housekeeping genes. Other O. volvulus genes showed homology only to predicted genes from the free-living nematode Caenorhabditis elegans or were entirely novel. Some of the novel proteins contain potential secretory leaders. Secondly...
A scalable method for screening and selection of peptide-specific monoclonal antibodies (mAbs) is described. To identify high affinity anti-peptide mAbs in hybridoma supernatants, antibodies were captured by magnetic affinity beads followed by binding of specific peptides from solution. After timed washing steps, the remaining bound peptides were eluted from the beads and detected by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). This allowed measurement of monovalent interactions of peptides with single antigen binding sites on the antibodies, thus reflecting antibody affinity rather than avidity. Antibodies that were able to bind target peptides from solution phase and retain them during washing for a minimum of 10 minutes were identified by the strength of the appropriate m/z peptide MS signals obtained. This wash time reflects the minimum peptide dissociation time required for use of these antibodies in several current immuno-mass spectrometry assays. Kinetic analysis of antibody-peptide binding by surface plasmon resonance (SPR) showed that the selected antibodies were of high affinity and, most importantly, had low dissociation constants. This method, called MALDI immunoscreening (MiSCREEN)...
An approach was developed for the isolation and characterization of soybean plasma membrane-associated proteins by immunoscreening of a cDNA expression library. An antiserum was raised against purified plasma membrane vesicles. In a differential screening of approximately 500,000 plaque-forming units with the anti-(plasma membrane) serum and DNA probes derived from highly abundant clones isolated in a preliminary screening, 261 clones were selected from approximately 1,200 antiserum-positive plaques. These clones were classified into 40 groups by hybridization analysis and 5'- and 3'-terminal sequencing. By searching nucleic acid and protein sequence data bases, 11 groups of cDNAs were identified, among which valosin-containing protein (VCP), clathrin heavy chain, phospholipase C, and S-adenosylmethionine:delta 24-sterol-C-methyltransferase have not to date been cloned from plants. The remaining 29 groups did not match any current data base entries and may, therefore, represent additional or yet uncharacterized genes. A full-length cDNA encoding the soybean VCP was sequenced. The high level of amino acid identity with vertebrate VCP and yeast CDC48 protein indicates that the soybean protein is a plant homolog of vertebrate VCP and yeast CDC48 protein.
Anisakis simplex is a representative nematode parasitizing marine organisms, such as fish and squids, and causes not only anisakiasis but also IgE-mediated allergy. Although 10 kinds of proteins have so far been identified as A. simplex allergens, many unknown allergens are considered to still exist. In this study, a chemiluminescent immunoscreening method with higher sensitivity than the conventional method was developed and used to isolate IgE-positive clones from an expression cDNA library of A. simplex. As a result, three kinds of proteins, Ani s 11 (307 amino acid residues), Ani s 11-like protein (160 residues) and Ani s 12 (295 residues), together with three known allergens (Ani s 5, 6 and 9), were found to be IgE reactive. Furthermore, ELISA data showed that both recombinant Ani s 11 and 12 expressed in Escherichia coli are recognized by about half of Anisakis-allergic patients. Ani s 11 and Ani s 11-like protein are characterized by having six and five types of short repetitive sequences (5-16 amino acid residues), respectively. Both proteins share as high as 78% sequence identity with each other and also about 45% identity with Ani s 10, which includes two types of short repetitive sequences. On the other hand, Ani s 12 is also structurally unique in that it has five tandem repeats of a CX13-25CX9CX7...