Biomedical subjects
Publications and source records attributed to D V Rebrikov.
We overexpressed duplex-specific nuclease (DSN) from Kamchatka crab in Escherichia coli cells and developed procedures for purification, renaturation, and activation of this protein. We demonstrated identity of the properties of the native and recombinant DSN. We also successfully applied the recombinant DSN for full-length cDNA library normalization.
The existing diversity of the methods for detecting single nucleotide polymorphisms is so great that may perplex an unsophisticated researcher who chooses the appropriate molecular genetic toolkit. In this work, we tried to systematize and briefly describe the state-of-the-art methods for detecting oligonucleotide polymorphisms that are based on allele-specific PCR and hybridization with oligonucleotide probe as well as to characterize the methods considered with respect to their accuracy, cost, and simplicity.
Comparisons of bacterial genomes demonstrate that even strains of one species may strikingly differ in gene set. Strain-specific genes are of considerable interest, as they may be responsible for distinguishing features, such as virulence or drug resistance, of the strain and may be employed as markers in epidemiological or evolutionary studies. Suppression subtractive hybridization (SSH) was shown to be suitable for generating a set of DNA fragments differing between two closely related bacterial strains. More than 95% DNA fragments selected by SSH proved to be specific for Staphylococcus aureus strains ZW compared with strain 29213.
Suppression subtractive hybridization (SSH) is one of the most powerful and popular methods for isolating differentially expressed transcripts. However, SSH-generated libraries typically contain some background clones representing non-differentially expressed transcripts. To overcome this problem we developed a simple procedure that substantially decreases the number of background clones. This method is based on the following difference between target and background cDNAs: each kind of background molecule has only one orientation with respect to the two different flanking adapter sequences used in SSH, while truly differentially expressed target cDNA fragments are represented by both sequence orientations. The described method selects the molecules that arose due to hybridization of such mirror-orientated molecules. The efficiency of this method was demonstrated in both model and real experimental subtractions.
The glutamyl endopeptidase gene of Bacillus intermedius was cloned from a genomic library expressed in Bacillus subtilis and sequenced (EMBL accession number Y15136). The encoded preproenzyme contains 303 amino acid residues; the mature 23-kDa enzyme consists of 215 residues. The mature enzyme reveals 38% of identical residues when aligned with the glutamyl endopeptidase from Bacillus licheniformis, whereas only five invariant residues were found among all known glutamyl endopeptidases. The amino acid residues that form the catalytic triad (H47, D98, and S171) as well as H186 participating in the binding of the substrate carboxyl group were identified. It seems that the structural elements responsible for the function of glutamyl endopeptidases from various sources are highly variable.
A new cryI-related sequence designated cryIM was cloned using an immunoscreening technique from ssp. wuhanensis of Bacillus thuringiensis (BT), previously reported to produce multiple Cry proteins [Chestukhina et al. (1994) Can. J. Microbiol. 240, 1026-1034]. Analysis of the cryIM nucleotide sequence revealed an ORF, BTII-type promoter-like sequence, peculiar for such genes, a translation initiation element and a putative transcription terminator. Nevertheless, its product was not previously found in the crystals of the host strain [Chestukhina et al. (1994) Can. J. Microbiol. 240, 1026-1034] which shows its weak or absent natural expression. The amino acid sequence of 1151 residues encoded by the continuous reading frame of cryIM is not identical but is essentially similar to the other delta-endotoxins of the CryI class. An IS231-like sequence was found 400 bp downstream of the cryIM stop codon and a fragment of the cryIAb gene was located 3 kb upstream of its initiator codon in the same orientation. Artificial expression of the cloned gene in E. coli under the control of the lacZ promoter allowed us to obtain its hypothetical protein product.
Trypsin from hepatopancreas of the Paralithodes camtschaticus crab was isolated in homogeneous state by successive ion-exchange chromatography on DEAE-Sephadex, affinity chromatography on Agarose modified with peptide ligands from trypsin hydrolysate of salmin, and ion-exchange chromatography on a Mono Q column. The total yield of the protein was 64%. Its N-terminal amino acid sequence was determined (IVGGTEVTPG-). A sample of amplified total cDNA of hepatopancreas of king crab was obtained. The cDNA fragment containing the complete coding part of the gene was isolated on the basis of the known N-terminal amino acid sequence of the mature form of the trypsin. The polypeptide chain of the proenzyme consists of 266 aa. The mature trypsin involves 237 aa, which corresponds to its molecular mass of 24.8 kDa. A comparison of the amino acid sequence of the king crab trypsin with those of trypsins from other species of crustaceans demonstrated their high structural homology. The trypsin from the Penaeus vannamei shrimp appeared to be the most close in its primary structure to that of the king crab (70% identity).
A combination of suppression subtraction hybridization (SSH) and a new technique of mirror orientation selection (MOS) was used to compare the total DNA for two, sexual (SR) and asexual (AR), races of freshwater planarian Giradia tigrina. Several race-specific DNA fragments were found. A new element termed planarian extrachromosomal virus-like element (PEVE) was revealed in AR. The PEVE genome contains two unique regions, Ul and Us, which are flanked by inverted repeats. Two variants observed for the PEVE genome differ in combination of single- and double-stranded regions corresponding to Ul and Us. The PEVE genome codes for two helicases, one homologous to the circovirus replication initiation protein (Rep) and one corresponding to the helicase domain of papillomavirus E1. PEVE is nonuniformly distributed though the planarian body and is possibly replicated only in certain parenchymal cells.
The accuracy of a real-time polymerase-chain-reaction assay for genetically modified sources in food products was determined using two official test systems (kits) of primers and samples. These kits were recommended by the Federal Center of State Sanitary and Epidemiological Surveillance (Russian Ministry of Health) and the European Commission. We used the following three models of thermocyclers: iCycler iQ (BioRad, United States), Rotor-Gene 3000 (Corbett Research, Australia), and DT-322 (DNA-Technology, Russia). Studies of samples that contained 1% genetically modified sources showed that the error of a quantitative assay for genetically modified sources in food products corresponds to 20-30% and does not depend on the kit type and the thermocycler model used.
The registration of the accumulation of polymerase chain reaction (PCR) products in the course of amplification (real-time PCR) requires specific equipment, i.e., detecting amplifiers capable of recording the level of fluorescence in the reaction tube during amplicon formation. By the time the reaction is completed, researchers obtain DNA accumulation graphs. The review discusses the most promising algorithms of analysis of real-time PCR curves and possible errors, whether caused by the software used or the operators' mistakes. The data included will assist researchers in understanding the features of the method to obtain more reliable results.
The main physicochemical characteristics of the major isoform of the laccase secreted by the fungu, Trametes hirsuta 072 were studied. The enzyme belongs to the group of high redox potential laccases (E(T1) = 790 +/- 5), and it oxidizes with high efficiency various substrates of phenolic nature. The gene of this isoform was cloned, and its nucleotide sequence was determined. The length of the complete gene is 2134 bp. It comprises 11 exons and 10 introns. Analysis of the amino acid sequence of T. hirsuta 072 laccase demonstrated a high homology (to 96.9%) to the other laccases secreted by fungi of the genus Trametes.
The digestion of the milk sugar (lactose) is observed every normal child but not in every adult. The decreased lactase synthesis in some adults results in problems with digestion of the whole milk (primary hypolactasy). An association of lactase activity in adults with carrying of the allele T within the polymorphism C/T-13910 located upstream of the lactase gene and 100% association of hypolactasy with the genotype C/C has recently been shown for a Finnish sample. In the present work we determined the LCT* C/T_13910 genotypes and allele frequencies in populations from Russia. The genotype C/C frequencies varied from 36.6% for Russians to 88.2% for Chukchi and were close to the published medical and epidemiological data on hypolactasy frequencies in respective populations. Genotyping was performed by three different methods to identify the optimal one. Our results have shown that the studied locus is the key determinant for the primary hypolactasy development in various human populations. Consequently, the DNA diagnostics of the C/C genotype carrying is a promising predictive test to detect the primary hypolactasy long before its clinical development. Practical application of this type of diagnostics would be a step towards the individual-oriented medicine.