Molecular cloning, purification and immunological responses of recombinants GroEL and DnaK from Streptococcus pyogenes

To better understand the roles of heat shock proteins in streptococcal diseases, the groEL and dnaK genes from Streptococcus pyogenes were cloned and their products (GroEL and DnaK) and derivatives (F2GroEL, F3GroEL and C1DnaK) purified as His-tagged fusion proteins. Western blot analysis of the purified proteins with sera from individuals with streptococcal diseases demonstrated that 29 out of 36 sera tested were reactive with GroEL and eight recognized DnaK. Rabbit antiserum against myosin recognized both GroEL and DnaK. Antibodies raised against purified F2GroEL and DnaK reacted with myosin in the ELISA but not in a Western immunoblot. These data indicate that the S. pyogenes GroEL and DnaK may be important immunogens during streptococcal infections. Furthermore, we provide evidence of an immunogenic relatedness of the GroEL and DnaK proteins with myosin that could play a role in the pathogenesis of streptococcal non-suppurative sequelae.     

Molecular cloning and functional characterization of a novel decarboxylase from uncultured microorganisms

The metagenomic library approach has been used successfully to isolate novel biocatalyst genes from uncultured microorganisms. We report the cloning of a novel decarboxylase gene by sequence-based screening of a plasmid metagenomic library constructed with DNA from alkaline polluted soils. The gene was named undec1 A and had an open reading frame of 1077 base pairs. It encoded a 359 amino acid polypeptide with a molecular mass of 38 kDa. The predicted protein had 58% similarity to a decarboxylase from Chlorobium phaeobacteroides BS1. The putative decarboxylase gene was subcloned into pETBlue-2 vector and overexpressed in Escherichia coli Tuner (DE3) pLac. The recombinant protein was purified to homogeneity. Functional characterization with liquid chromatography-mass spectrometry confirmed that the recombinant Undec1 A protein catalyzed the decarboxylation of L-cysteine to form cysteamine.     

M.SpyI, a DNA methyltransferase encoded on a mefA chimeric element, modifies the genome of Streptococcus pyogenes

While screening the clonality of Streptococcus pyogenes isolates from an outbreak of erythromycin-resistant pharyngitis in Pittsburgh, PA, we found a correlation between the presence of the chimeric element Phi10394.4 (carrying the macrolide efflux gene, mefA) and genomic DNA being resistant to cleavage by SmaI restriction endonuclease. A search of the open reading frames in Phi10394.4 identified a putative type II restriction-modification (R-M) cassette containing a cytosine methyltransferase gene (spyIM). Heterologous expression of the cloned spyIM gene, as well as allelic-replacement experiments, showed that the action of this methyltransferase (M.SpyI) was responsible for the inhibition of SmaI digestion of genomic DNA in the Phi10394.4-containing isolates. Analysis of the methylation patterns of streptococcal genomic DNA from spyIM-positive strains, a spyIM deletion mutant, and a spyIM-negative strain determined that M.SpyI specifically recognized and methylated the DNA sequence to generate 5'-C(m)CNGG. To our knowledge, this is the first methyltransferase gene from S. pyogenes to be cloned and to have its activity characterized. These results reveal why pulsed field gel electrophoresis analysis of SmaI-digested genomic DNA cannot be used to analyze the clonality of some streptococci containing Phi10394.4 and may explain the inability of previous epidemiological studies to use SmaI to analyze DNAs from macrolide-resistant streptococci. The presence of the SpyI R-M cassette in Phi10394.4 could impart a selective advantage to host strain survival and may provide another explanation for the observed increase in macrolide-resistant streptococci.     

Helper plasmid cloning in Streptococcus sanguis: cloning of a tetracycline resistance determinant from the Streptococcus mutans chromosome

A model system for testing the helper plasmid cloning system of Gryczan et al. (Mol. Gen. Genet. 177:459-467, 1980) was devised for the Streptococcus sanguis (Challis) host-vector system. In this system, linearized pVA736 plasmid efficiently transformed an S. sanguis (Challis) host containing a homologous plasmid, pVA380-1, but did not transform a plasmidless host or a host containing a nonhomologous plasmid, pVA380. In addition, whereas monomeric circular pVA736 transformed a plasmidless host with two-hit kinetics, it transformed a pVA380-1-containing host with one-hit kinetics. This helper plasmid cloning system was used to isolate two HindIII fragments (5.0 megadaltons [Mdal] and 1.9 Mdal in size) from the chromosome of Streptococcus mutans V825 which conferred high-level tetracycline resistance. One tetracycline-resistant clone was examined and found to contain three plasmids which were sized and designated pVA868 (9.0 Mdal), pVA869 (9.5 Mdal), and pVA870 (9.8 Mdal). Results of Southern blot hybridization and restriction endonuclease digestion confirmed that all three chimeras were composed of two HindIII fragments of the S. mutans V825 chromosome, as well as a large portion, varying in size for each chimera, of the 2.8 Mdal cloning vector, pVA380-1. Incompatibility observed between pVA380-1 and each of the chimeras indicated that replication of the chimeras was governed by the pVA380-1 replicative origin. Southern blotting experiments revealed that the chimeras hybridized to Tn916, providing the first evidence that transposon-related genes of enteric streptococcal origin are disseminated among oral streptococci.     

Molecular cloning, sequence analysis, and functional expression of a novel growth regulator, oncostatin M.

Oncostatin M is a polypeptide of Mr approximately 28,000 that acts as a growth regulator for many cultured mammalian cells. We report the cDNA and genomic cloning, sequence analysis, and functional expression in heterologous cells of oncostatin M. cDNA clones were isolated from mRNA of U937 cells that had been induced to differentiate into macrophagelike cells by treatment with phorbol 12-myristate 13-acetate, and a genomic clone was also isolated from human brain DNA. Sequence analysis of these clones established the 1,814-base-pair cDNA sequence as well as exon boundaries. This sequence predicted that oncostatin M is synthesized as a 252-amino-acid polypeptide, with a 25-residue hydrophobic sequence resembling a signal peptide at the N terminus. The predicted oncostatin M amino acid sequence shared no homology with other known proteins, but the sequence of the 3' noncoding region of the cDNA contained an A + T-rich stretch with sequence motifs found in the 3' untranslated regions of many cytokine and lymphokine cDNAs. Oncostatin M mRNA of approximately 2 kilobase pairs was detected in phorbol 12-myristate 13-acetate-treated U937 cells and in activated human T cells. Transfection of cDNA encoding the oncostatin M precursor into COS cells resulted in the secretion of proteins with the structural and functional properties of oncostatin M. The unique amino acid sequence, expression by lymphoid cells, and growth-regulatory activities of oncostatin M suggest that it is a novel cytokine.     

Identification of SpyA, a novel ADP-ribosyltransferase of Streptococcus pyogenes

Streptococcus pyogenes, the aetiological agent of both respiratory and skin infections, produces numerous exotoxins to establish infection. This report identifies a new exotoxin produced by this organism, termed SpyA, for S. pyogenesADP-ribosylating toxin. SpyA, MW 24.9, has amino acid identity with the ADP-riboslytransferases (ADPRTs) Staphylococcus aureus EDIN and Clostridium botulinum C3. Recombinant SpyA was able to hydrolyse beta-NAD(+), and this activity was dependent on a glutamate at position 187. SpyA has a putative biglutamate active site, and similar to most biglutamate ADPRTs, was able to ADP-ribosylate poly-l-arginine. SpyA modified numerous proteins in both CHO and HeLa cell lysates. Two-dimesional gel analysis and MALDI-TOF MS analysis of modified proteins indicated that vimentin, tropomyosin and actin, all cytoskeletal proteins, are targets. Expression of spyA in HeLa cells resulted in loss of actin microfilaments. We hypothesize that SpyA is produced by S. pyogenes to disrupt cytoskeletal structures and promote colonization of the host.     

Molecular cloning and functional analysis of a novel Cx43 partner protein CIP150

We identified and cloned a novel gene encoding a partner protein, CIP150, of connexin 43 (Cx43). CIP150 associates with Cx43 through its carboxyl terminal domain. Conversely, a region consisting of 16 amino acids in the juxtamembrane region (amino acids 227-242) in the carboxyl terminal tail of Cx43 was identified to be responsible for the association. A variant of Cx43 lacking this region was expressed only in a nonphosphorylated form and appeared to lose the capacity to localize to the region of cell-cell contact and dye transfer activity. When the expression of CIP150 was suppressed using small interfering RNA, the localization to the plasma membrane as well as dye transfer activity of Cx43 was significantly reduced. These results suggest that the newly identified domain is essential for the proper phosphorylation and localization of Cx43, and CIP150 is a novel partner protein targeting this domain.     

Molecular cloning,expression, and functional characterization of a novel zebrafish cytosolic sulfotransferase

By searching the zebrafish expressed sequence tag (EST) database, we have identified a cDNA clone encoding a putative zebrafish cytosolic sulfotransferase (ST). This cDNA was isolated and subjected to nucleotide sequencing. Analysis of the sequence data revealed that this novel zebrafish ST displays 32-35% amino acid sequence identity to members of all major cytosolic ST gene families. Therefore, this zebrafish ST, while belonging to the cytosolic ST gene superfamily, appears to be independent from all known constituent ST gene families. Recombinant zebrafish ST, expressed using the pET23c prokaryotic expression vector and purified from transformed Escherichia coli cells, migrated as a 34-kDa protein upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Purified zebrafish ST displayed sulfating activities toward dopamine and thyroid hormones (T(3) and T(4)), with a pH optimum spanning 7-9. The enzyme also exhibited activities toward a number of xenobiotics including some flavonoids, isoflavonoids, and other phenolic compounds. A thermostability experiment revealed the enzyme to be relatively stable over a temperature range between 20 and 48 degrees C. Among 10 divalent metal cations tested, Fe(++), Hg(++), Co(++), Zn(++), Cu(++), and Cd(++) exhibited dramatic inhibitory effects on the activity of the enzyme. These results constitute a first study on the cloning, expression, and characterization of a zebrafish cytosolic ST.     

Molecular cloning, functional analysis and localization of a novel gene encoding polygalacturonase-inhibiting protein in Chorispora bungeana

Polygalacturonase-inhibiting proteins (PGIPs) are plant defense proteins. To date, no spatial distribution of PGIPs and interaction between PGIPs and nitric oxide (NO) in plant were described. Here, we first reported the full-length cDNA sequence of PGIP of Chorispora bungeana (CbPGIP1). Notably, immunofluorescence localization showed that the CbPGIP was evenly distributed in leaves but it was mainly localized in epidermis and vascular bundle in stems and roots. Further studies indicated that CbPGIP had higher abundance in roots than in stems and leaves. Conversely, the bulk PGIP of C. bungeana showed a higher activity in leaves than in stems and roots. In addition, quantitative real-time polymerase chain reaction demonstrated that CbPGIP1 expression was induced by Stemphylium solani, salicylic acid (SA), 4, ?4°C and NO. This is a first report attempting to predict if NO can induce the PGIP expression. Taken together, these findings showed that the gene was spatially regulated and NO and SA might take part in CbPGIP1 expression induced by biotic and abiotic stresses. This study highlighted the potential importance of CbPGIP1 and NO in plant resistance.     

Molecular characterization of a novel fibronectin-binding protein of Streptococcus pyogenes strains isolated from toxic shock-like syndrome patients

Group A Streptococcus pyogenes has surface-located fibronectin (Fn)-binding proteins known to be a major virulence factor, which adheres to and invades host cells. We present a novel Fn-binding protein of group A streptococcus serotype M3 and M18 strains isolated from patients with toxic shock-like syndrome (TSLS). By searching the whole genome sequence of an M3 strain from a TSLS patient, an open reading frame was found among the putative surface proteins. It possessed an LPXTG motif and Fn-binding repeat domains in the C-terminal region and was designated as FbaB (Fn-binding protein of group A streptococci type B). The fbaB gene was found in all M3 and M18 strains examined, although not in other M serotypes. Furthermore, FbaB protein was expressed on the cell surface of TSLS strains but not on non-TSLS ones. Enzyme-linked immunosorbent assay and ligand blotting revealed that recombinant FbaB exhibits a strong Fn-binding ability. An FbaB-deficient mutant strain showed 6-fold lower adhesion and invasion efficiencies to HEp-2 cells than the wild type. Moreover, mortality was decreased in mice infected with the mutant strain in comparison to the wild type. These data suggest that FbaB is etiologically involved in the development of invasive streptococcal diseases.     

Ceramide kinase, a novel lipid kinase. Molecular cloning and functional characterization

Ceramide-1-phosphate is a sphingolipid metabolite that has been implicated in membrane fusion of brain synaptic vesicles and neutrophil phagolysosome formation. Ceramide-1-phosphate can be produced by ATP-dependent ceramide kinase activity, although little is known of this enzyme because it has not yet been highly purified or cloned. Based on sequence homology to sphingosine kinase type 1, we have now cloned a related lipid kinase, human ceramide kinase (hCERK). hCERK encodes a protein of 537 amino acids that has a catalytic region with a high degree of similarity to the diacylglycerol kinase catalytic domain. hCERK also has a putative N-myristoylation site on its NH(2) terminus followed by a pleckstrin homology domain. Membrane but not cytosolic fractions from HEK293 cells transiently transfected with a hCERK expression vector readily phosphorylated ceramide but not sphingosine or other sphingoid bases, diacylglycerol or phosphatidylinositol. This activity was clearly distinguished from those of bacterial or human diacylglycerol kinases. With natural ceramide as a substrate, the enzyme had a pH optimum of 6.0-7.5 and showed Michaelis-Menten kinetics, with K(m) values of 187 and 32 microm for ceramide and ATP, respectively. Northern blot analysis revealed that hCERK mRNA expression was high in the brain, heart, skeletal muscle, kidney, and liver. A BLAST search analysis using the hCERK sequence revealed that putative ceramide kinases (CERKs) exist widely in diverse multicellular organisms including plants, nematodes, insects, and vertebrates. Phylogenetic analysis revealed that CERKs are a new class of lipid kinases that are clearly distinct from sphingosine and diacylglycerol kinases. Cloning of CERK should provide new molecular tools to investigate the physiological functions of ceramide-1-phosphate.     

化脓性链球菌脂蛋白FtsB的基因克隆、表达、纯化与功能研究

体外克隆化脓性链球菌5005的tsb基因,表达并纯化FtsB蛋白,并对其铁色素结合特性进行初步研究.首先通过PCR方法从基因组中扩增ftsb基因,将其连接到pGEX4T-1载体上,转入大肠杆菌DH5a中大量扩增,将测序正确的重组载体转化到表达宿主大肠杆菌BL21进行表达,优化诱导表达条件.利用亲和层析方法纯化表达产物,并对FtsB的铁色素结合特性进行研究,同时通过DEPC封闭组氨酸实验对其结合位点进行初步研究.成功构建原核表达载体pGEX-ftsb,获得分子量约33 kD的野生型FtsB蛋白,产率为30 mg/L.紫外-可见光谱研究表明FtsB和铁色素结合后在450 nm处出现紫外吸收峰,DEPC封闭组氨酸实验证明FtsB中组氨酸不参与铁色素的结合.对FtsB蛋白进行铁色素结合特性和结合位点进行研究,为进一步研究细菌中的铁色素转运机理及开发疫苗候选物和药靶奠定一定的理论基础.     

Cloning and characterization of two novel DNases from Streptococcus pyogenes

The proteins in the culture supernatant (exoproteins) from Streptococcus pyogenes serotype M1 were separated by two-dimensional gel electrophoresis, and their N-terminal amino acid sequences were determined. The amino acid sequences were compared to sequences in the S. pyogenes genome database. The coding sequence showed similarity to sequences of two genes, mf2-v ( mf2 variant) and mf3, which had sequence similarity to genes encoding mitogenic factor (MF); MF has DNase activity. The recombinant genes were expressed in Escherichia coli and the proteins were synthesized. Mf2-v and Mf3 had DNase activity. The activity of Mf2-v was localized to the C-terminal half of the protein. The mf3 gene was shown to be present in most clinically isolated strains of S. pyogenes tested, and the mf2gene was detected in 20% of the isolates. The products of the mf2 and mf3 genes in clinically isolated S. pyogenes strains were thus shown to be DNases.     

Replication origin of Streptococcus pyogenes, organization and cloning in heterologous systems

The origin of DNA replication (oriC) of Streptococcus pyogenes, group A streptococci (GAS), has been cloned in Escherichia coli and reintroduced by transformation into other GAS strains. Transformation frequencies into GAS strains with oriC-carrying plasmids occurred with unusually high frequencies. However, the oriC-containing plasmids in the new recipients were found to be unstable and had a tendency to integrate into the chromosome, even when a recA GAS strain was used as a recipient. The GAS oriC was able to direct the replication of autonomous plasmids in group B streptococcal recipients. The chromosomal organization of the oriC region of GAS relative to other bacterial species appears to be similar to oriC of Bacillus subtilis and other Gram-positive microorganisms.