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I I Nikolskaya

Publications and source records attributed to I I Nikolskaya.

At least 19 recordsLinked to original sources
PubMed2001

Characterization of bovine atrial angiotensin-converting enzyme.

Bovine atrial angiotensin-converting enzyme (ACE) was purified to electrophoretic homogeneity. The purification procedure included ion-exchange chromatography on DEAE-Toyopearl 650M, affinity chromatography on lisinopril-agarose and gel filtration on Sephadex G-100. The bovine atrial ACE exhibited similar sensitivities to inhibition by lisinopril and captopril as lung ACE (the Ki values for the atrial and lung enzymes differed insignificantly). However, the kinetic parameters of hydrolysis of some synthetic tripeptide substrates (FA-Phe-Gly-Gly, FA-Phe-Phe-Arg, Cbz-Phe-His-Leu, Hip-His-Leu) catalyzed by bovine atrial and lung ACE varied to a greater extent. The enzymes were also characterized by some differences in activation by chloride, nitrate, and sulfate anions. These data support the hypothesis of tissue specificity of ACEs.

Animals↗
PubMed2000

Isolation and characterization of the N-domain of bovine angiotensin-converting enzyme.

A method for preparation of a catalytically active fragment of bovine lung angiotensin-converting enzyme (ACE) has been developed. It includes limited proteolysis of the full-length somatic form of the enzyme by trypsin. The resulting fragment corresponds to the N-terminal domain of angiotensin-converting enzyme. The influence of chloride and sulfate anions on the enzymatic activity of this fragment has been investigated, and kinetic parameters for hydrolysis of synthetic tripeptide substrates catalyzed by the N-domain of ACE have been determined. Comparison of these parameters with those obtained for full-length somatic bovine ACE suggests that in the bovine somatic ACE molecule active centers located in various domains may function interdependently.

Animals↗
PubMed1999

Structural organization of membrane and soluble forms of somatic angiotensin-converting enzyme.

The catalytic activity and quaternary structure of soluble (s) and membrane (m) forms of angiotensin-converting enzyme (ACE) were studied in reversed micelles of ternary system Aerosol OT--water--octane. The profile of the dependence of the catalytic activity of the two enzyme forms on the degree of surfactant hydration (micellar size) had several optima corresponding to the function of various active oligomeric enzyme forms; the curves for the s- and m-forms of ACE were different. Data of sedimentation analysis prove that in reversed micelles, s-ACE can exist as monomers, dimers, or tetramers depending on the hydration degree, and the m-form is present as dimers and tetramers only. The values of the kinetic parameters for the hydrolysis of the substrate furylacryloyl-Phe-Gly-Gly by all the enzyme forms were determined, and the data indicate that the activity of the m-form is enhanced by oligomerization. The ACE activity strongly depends on the medium; it is higher when ACE is in contact with matrix or other enzyme molecules.

Catalysis↗
PubMed1999

Inhibitor analysis of angiotensin I-converting and kinin-degrading activities of bovine lung and testicular angiotensin-converting enzyme.

Inhibition of bovine lung and testicular angiotensin-converting enzyme (ACE) by some well-known ACE inhibitors (lisinopril, captopril, enalapril), new substances (Nalpha-carboxyalkyl dipeptides PP-09, PP-35, and PP-36), and phosphoramidon was investigated using Cbz-Phe-His-Leu and FA-Phe-Phe-Arg (C-terminal analogs of angiotensin I and bradykinin, respectively) as the substrates. The somatic (two domains) and testicular (single domain) isoenzymes demonstrated different kinetic parameters for hydrolysis of these substrates. All of the inhibitors were competitive inhibitors of both ACE isoforms, and the Ki values were substrate-independent. The relative potencies of the inhibitors for both enzymes were: lisinopril > captopril > PP-09 > enalapril > PP-36 > PP-35 > phosphoramidon. The inhibition efficiency of PP-09 was comparable with those of the well-known ACE inhibitors. Captopril was more effectively bound to the somatic ACE (Ki = 0.5 nM) than to the testicular isoform (Ki = 6.5 nM).

Angiotensin I↗
PubMed1998

Carbohydrates regulate the dimerization of angiotensin-converting enzyme.

Regulation of the catalytic activity and supramolecular structure of angiotensin-converting enzyme was studied in reverse micelles of Aerosol OT in octane as biomembrane model. The kinetic experiments and the sedimentation analysis demonstrated that the enzyme can function both in monomeric and dimeric form. The degree of dimerization was strongly dependent on the concentration and structure of mono- and disaccharides added to the media, indicating the specific role of carbohydrates in forming the supramolecular structure of angiotensin-converting enzyme. The existence of carbohydrate-binding center on the enzyme molecule is proposed.

Animals↗
PubMed1997

Purification of soluble and membrane forms of somatic angiotensin-converting enzyme by cascade affinity chromatography.

Soluble and membrane forms of angiotensin-converting enzyme were purified by cascade affinity chromatography. The enzyme forms were completely separated from each other using their different affinity to the hydrophobic matrix phenyl-silochrome. The enzymes was further purified on affinity sorbent prepared by immobilization of the enzyme inhibitor N-[1(S)-carboxy-5-aminopentyl]glycylphenylalanine on agarose. The procedure yielded electrophoretically homogeneous soluble and membrane forms of angiotensin-converting enzyme containing only active molecules as demonstrated by titration with the reversible inhibitor lisinopril. According to phase separation in the presence of Triton X-114, the membrane enzyme is more hydrophobic than the soluble form. The catalytic characteristics of the enzyme forms differed from each other in the system Aerosol OT-water-octane (reversed micelles) which is model for the membrane environment of the enzymes in vivo.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

Cross-linking of SsoII restriction endonuclease to cognate and non-cognate DNAs.

Specific and non-specific interactions of SsoII restriction endonuclease (R.SsoII) were probed by the method of covalent attachment to modified DNA containing an active monosubstituted pyrophosphate internucleotide bond instead of a phosphodiester one. R.SsoII with six N-terminal His residues was shown to be cross-linked to duplexes with this type of modification, either containing or not the recognition sequence. Competition experiments with covalent attachment of R.SsoII to activated DNAs demonstrated the similar affinity of the enzyme to cognate and non-cognate DNAs in the absence of cofactor, Mg2+ ions.

Base Sequence↗
PubMed1995

The interaction of DNA duplexes containing 2-aminopurine with restriction endonucleases EcoRII and SsoII.

Oligonucleotides containing 2-aminopurine (2-AP) in place of G or A in the recognition site of EcoRII (CCT/AGG) or SsoII (CCNGG) restriction endonucleases have been synthesized in order to investigate the specific interaction of DNA with these enzymes. Physicochemical properties (CD spectra and melting behaviour) have shown that DNA duplexes containing 2-aminopurine exist largely in a stable B-like form. 2-Aminopurine base paired with cytidine, however, essentially influences the helix structure. The presence of a 2-AP-C mismatch strongly reduces the stability of the duplexes in comparison with the natural double strand, indicated by a biphasic melting behaviour. SsoII restriction endonuclease recognizes and cleaves the modified substrate with a 2-AP-T mismatch in the centre of the recognition site, but it does not cleave the duplexes containing 2-aminopurine in place of inner and outer G, or both. EcoRII restriction endonuclease does not cleave duplexes containing 2-aminopurine at all. The two-substrate mechanism of EcoRII-DNA interaction, however, allows hydrolysis of the duplex containing 2-aminopurine in place of adenine in the presence of the canonical substrate.

2-Aminopurine↗
PubMed1995

The SsoII and NlaX DNA methyltransferases: overproduction and functional analysis.

Overproduction of the NlaX DNA methyltransferase (M.NlaX) in an Escherichia coli host conferred resistance to SsoII restriction endonuclease (R.SsoII) digestion. This suggested an overlap of sequence specificity between M.NlaX and M.SsoII, the latter of which modifies the internal cytosine of the target sequence 5'-CCNGG-3'. A variant of M.NlaX (M.Sso/Nla), containing an N-terminal extension from M.SsoII, was also enzymatically active. Using deletion analysis, the N-terminal 71 amino-acid residues of M.SsoII were shown to be essential for modification activity.

Amino Acid Sequence↗
PubMed1995

Interaction of the MvaI and SsoII methyltransferases with DNAs altered at the central base pair of the recognition sequence.

The interaction of the MvaI and SsoII DNA methyltransferases (MTases; M.MVaI and M.SsoII, respectively) with a set of synthetic DNA duplexes, containing a M.MvaI and M.SsoII recognition site (CCWGG), was investigated. In these DNA duplexes dA or dT of the recognition site was replaced by nucleoside analogs with modified sugar moieties and heterocyclic bases (2'-deoxy-2'-fluorouridine (flU), 1-(beta-D-2'-deoxy-threo-pentofuranosyl)thymine (xT), 1-(beta-D-3'-deoxy-threo-pentofuranosyl)uracil (tU)), or by 1,3-propanediol (Prd). A new approach for monitoring methylation of each strand of DNA duplexes by MTases was developed. It allowed the determination of the influence of the modification in one DNA strand on the methylation of the other. In most cases, for both M.MvaI and M.SsoII, sugar analog-containing duplexes showed inhibition of methylation of only the modified strand. Prd-containing DNA duplexes were not substrates for M.MvaI. M.SsoII did not methylate DNA duplexes in which the dT residue was replaced by Prd.

Amino Acid Sequence↗
PubMed1993

Analysis of the nucleotide and derived amino acid sequences of the SsoII restriction endonuclease and methyltransferase.

A 2648-bp fragment from the P4 plasmid of Shigella sonnei strain 47 coding for the SsoII restriction endonuclease (ENase) and methyltransferase (MTase) (recognition sequence 5'-CCNGG) was sequenced. Two divergently arranged open reading frames of 905 bp for the SsoII ENase (R.SsoII) and 1137 bp for the MTase (M.SsoII) were identified. The coding regions are separated by 110 bp. The calculated M(r) of R.SsoII (35937) and M.SsoII (42887) are in good agreement with values previously obtained by in vitro transcription-translation experiments, i.e., 35 and 43 kDa for the ENase and MTase, respectively. The M.SsoII amino acid (aa) sequence revealed a considerable similarity to m5C-MTases recognizing the related sequences--M.EcoRII, M.dcm, M.MspI, M.BsuFI, M.HpaII, and M.HhaI. Surprisingly, the greatest degree of homology has been observed between the aa sequences of M.SsoII and M.NlaX, with an unidentified recognition sequence. The multiple alignment of aa sequences helps to identify the blocks of conserved aa in variable regions of MTases. These conserved aa can play a key role in target recognition. Some aspects of evolution of m5C-MTases are discussed.

Amino Acid Sequence↗
PubMed1992

Cleavage of synthetic substrates containing non-nucleotide inserts by restriction endonucleases. Change in the cleavage specificity of endonuclease SsoII.

A study was made of the interaction between restriction endonucleases recognizing CCNGG (SsoII and ScrFI) or CCA/TGG (MvaI and EcoRII) DNA sequences and a set of synthetic substrates containing 1,3-propanediol, 1,2-dideoxy-D-ribofuranose or 9-[1'-hydroxy-2'-(hydroxymethyl)ethoxy] methylguanine (gIG) residues replacing either one of the central nucleosides or dG residues in the recognition site. The non-nucleotide inserts (except for gIG) introduced into the recognition site both increase the efficiency of SsoII and change its specificity. A cleavage at the noncanonical position takes place, in some cases in addition to the correct ones. Noncanonical hydrolysis by SsoII occurs at the phosphodiester bond adjacent to the point of modification towards the 5'-end. With the guanine base returned (the substrate with gIG), the correct cleavage position is restored. ScrFI specifically cleaves all the modified substrates. DNA duplexes with non-nucleotide inserts (except for the gIG-containing duplex) are resistant to hydrolysis by MvaI and EcoRII. Prompted by the data obtained we discuss the peculiarities of recognition by restriction endonucleases of 5-membered DNA sequences which have completely or partially degenerated central base pairs. It is suggested that SsoII forms a complex with DNA in an 'open' form.

Base Sequence↗
PubMed1990

Characterization of the genetic determinants of SsoII-restriction endonuclease and modification methyltransferase.

The genes encoding SsoI and SsoII restriction endonuclease (ENase) and methyltransferase (MTase) are located on the small plasmids P6 and P4, respectively, of Shigella sonnei strain 47. Functions provided by plasmids P5, P7 and P9, which include colicinogenicity and immunity to colicin E1, resistance to streptomycin (Sm), and conjugative DNA transfer, respectively, have also been identified. The genes of the SsoII restriction-modification (R-M) system have been cloned into Escherichia coli expressing the 35-kDa (ENase) and 43-kDa (MTase) products. A restriction map of the P4 plasmid DNA was determined, and the approximate location of the genes encoding SsoII ENase and MTase (ssoIIR and ssoIIM) on that have been established. SsoI is an isoschisomer of EcoRI and SsoII cleaves the 5'-/CCNGG/recognition sequence producing 5'-protruding 5-nt long cohesive ends.

Cloning, Molecular↗
PubMed1985

Sequence specificity of isolated DNA-adenine methylases from Mycobacterium smegmatis (butyricum) and Shigella sonnei 47 cells.

A set of four individual DNA-adenine methylases differing in pI (isoelectric point) values (MMbu4.2, MMbu6.4, MMbu7.3, and MMbu8.7), and a sole methylating enzyme with the same base specificity (MSso9.5) are present in M. smegmatis (butyricum) and Sh. sonnei 47 cells, respectively. The sequence specificity of each of those was studied 'in vitro' by a combined approach that comprised isostich (purine tract) analysis and identification of the immediate neighbourhood of the methylated base within the sequence methylated. The MSso9.5 recognition site has been established as the hexanucleotide 'palindromic' 5'-G-A-A-T-T-C-3' sequence which is structurally similar to the analogous MEco RI recognition site. However, in contrast to MEco RI, MSso9.5 methylates the 5'-end adenine residue in the sequence and thus it appears to be an isometimer of MEco RI. By means of the same approach, the partial nucleotide sequences methylated by each of the four individual M. butyricum enzymes were determined. MMbu7.3 and MMbu8.7 exhibit the identical sequence specificity upon methylation of the degenerative trinucleotide 5'-Py-A-Py-3' sequence and thus these enzymes are assumed to represent the different molecular forms of the methylase. MMbu4.2 methylates the 5'-G-G-A-3' sequence and thus it is of a great value as the tool for negating effects of the RBam HI and RAva II-type restriction. MMbu6.4 is of a particular interest on account of its unique DNA methylation pattern which is distinguished in the pronounced clustering of purine bases in the 5'-Pu-Pu-Pu-Pu-Pu-3' sequence methylated.

Base Sequence↗
PubMed1984

Sequence specificity of isolated DNA-cytosine methylases from Shigella sonnei 47 cells.

Five individual DNA-cytosine methylases differing in pI (isoelectric point) values are present in Shigella sonnei 47-cells. The sequence specificity of each of those was determined 'in vitro' by a highly efficient combined approach that included pyrimidine tract (isostic) analysis, identification of the immediate neighbourhood of the methylated base within the recognition sequence and the calculation method. The enzyme with pI 5.3 (MSso5.3) is the counterpart of the RSso 47 II in the Sso 47 II restriction-modification system and methylates the internal cytosine residue of the 'palindromic' 5'-C-C-N-G-G-3' sequence. The enzymes with pI 6.2 (MSso6.2) and 7.4 (MSso7.4) exhibit identical specificity upon methylation of the 'palindromic' 5'-Py-C-N-G-Pu-3' sequence, but differ in the pI values of the proteins. The enzyme with pI 4.2 (MSso4.2) recognizes the unique tetranucleotide 5'-C-C-C-C-3' sequence and methylates the second cytosine residue at the 5'-end of the sequence. The enzyme with pI 8.4 (MSso8.4) methylates the central cytosine residue within the degenerative trinucleotide 5'-(PuC)-C-C-3' sequence. MSso5.3, MSso6.2, and MSso7.4 are presumed to belong to the 'family' of sequence-specific (Eco RII-like) enzymes. These DNA-cytosine methylases are likely to be evolutionary related to Eco RII and to have undergone a sufficient genetic drift so as to recognize similar (but more degenerative) nucleotide sequences.

Base Sequence↗
PubMed1983

Isoelectric focusing of bacterial DNA methylases.

The multiplicity of bacterial DNA methylases has been shown for new microorganisms, Mycobacteria and Shigella, by a double-step procedure including column chromatography followed by isoelectric focusing of the total methylase fraction. The profiles of the DNA methylating activity of Sh. sonnei 47 and M. butyricum strains were studied. Sh. sonnei 47 cells were found to contain five different proteins responsible for DNA methylation and having pI 4.2, 5.3, 6.2, 8.4 and 9.2. Four M. butyricum methylases were represented by proteins with pI 4.2, 6.0, 8.0 and 9.0.

Chromatography, Affinity↗
PubMed1983

DNA-methylating activity of mycobacteria.

The methylating activity of the four mycobacterium strains Mycobacterium phlei, Mycobacterium smegmatis strain Butyricum, Mycobacterium smegmatis strain Rabinowitz, lysogenic Mycobacterium smegmatis strain Rabinowitz was studied in vitro. All the four strains were found to have methylating activity; enzyme containing extracts of M. smegmatis strain Butyricum and M. phlei showed a stronger activity than those of M. smegmatis strain Rabinowitz and the lysogenic Rabinowitz strain. The methylases of all the four strains methylated the adenine and cytosine residues of the acceptor DNA-forming 5-methyl-cytosine and 6-methyl-aminopurine. The mycobacterial DNAs were methylated by the corresponding mycobacterial methylases in vitro only to 25-30% as compared to the methylation on phage Sd-DNA. This is comparable with the low in vivo methylation of mycobacterial DNAs. The kinetics of methylation indicated a low non-specific nuclease content of the mycobacterium cells.

5-Methylcytosine↗