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V P Chuprina

Publications and source records attributed to V P Chuprina.

At least 19 recordsLinked to original sources
PubMed1998

Sequence-dependent binding of metal ion to DNA oligomeres. A comparison of molecular electrostatic potentials with NMR data.

Experimentally observed sequence-selective binding of metal ion to DNA oligonucleotides have been compared with variations of electrostatic potential (EP) along the helix. Calculations of EP have been performed for three atomic models of the oligonucleotide duplex [d(CGCGAATTCGCG)2] using several variants of EP calculations, including a solution of non-linear Poisson-Boltzmann equation (NPBE). N7 atom of guanine adjacent to adenine base was identified as a region with the most negative electrostatic potential in the major groove. The EP value for the Me ion binding site surpasses the value for N7 of other guanines by 10-26% depending on particular duplex conformation. Qualitatively, the sequence dependent variations of EP near guanine N7 atoms are in agreement with the sequence-selective behavior of Mn(II) and Zn(II) ions as revealed by NMR experiments. But the difference in EP between the two most negative regions near guanine N7 atoms does not exceed 1.25 kT/e. Simple model suggests that metal ions are capable to form ion-hydrate complexes with G-Pu steps of DNA duplex. These complexes are formed via one Me...G and five Me...water coordination bonds with water molecules hydrogen bonded to two adjacent purine bases in the same chain. We suppose that such a stereospecific structural possibility is the main factor which control the sequence-selectivity in the metal ion binding. A combination of both mechanisms allows to explain sequence specific Mn(II) and Zn(II) binding to a set of oligonucleotides.

Computer Simulation↗
PubMed1997

The study of possible A and B conformations of alternating DNA using a new program for conformational analysis of duplexes (CONAN).

A new program, CONAN has been designed for CONformational ANalysis of oligonucleotide duplexes with natural and modified bases. It allows to model both regular DNA fragments with different types of symmetry and irregular ones including bends, junctions, mismatched pairs and base lesions. Computations and minimization of the energy are performed in a space of internal structural variables chosen to build start structure easier and conveniently analyze the results obtained. These internal structural variables determine mutual base-base and base-sugar arrangement and sugar puckering. The analytical closure procedure is applied both to sugar rings and to backbone fragments between adjacent sugars. For more effective energy minimization, analytical gradient is calculated. The CONAN was applied to the search for low-energy conformations of poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC) duplexes. Extended regions of low-energy A and B conformations are revealed and characterized. These regions contain structures with different relative values of helical twist, tau, for pur-pyr and pyr-pur steps, namely, conformations with tau (pur-pyr) > tau (pyr-pur) and with tau (pur-pyr) < tau (pyr-pur). Two types of sugar puckering were found for B-form low-energy conformations, the first type with all C2'-endo sugar residues and the second one - with C2'-endo purines and O1'-endo pyrimidines. The calculated conformations are compared with X-ray diffraction data for crystals and fibers and NMR data for solution.

DNA↗
PubMed1995

Solution structure of the sequence-specific HMG box of the lymphocyte transcriptional activator Sox-4.

Two groups of HMG box proteins are distinguished. Proteins in the first group contain multiple HMG boxes, are non-sequence-specific, and recognize structural features as found in cruciform DNA and cross-over DNA. The abundant chromosomal protein HMG-1 belongs to this subgroup. Proteins in the second group carry a single HMG box with affinity for the minor groove of the heptamer motif AACAAAG or variations thereof. A solution structure for the non-sequence-specific C-terminal HMG box of HMG-1 has recently been proposed. Now, we report the solution structure of the sequence-specific HMG-box of the SRY-related protein Sox-4. NMR analysis demonstrated the presence of three alpha-helices (Val10-Gln22, Glu30-Leu41 and Phe50-Tyr65) connected by loop regions (Ser23-Ala49 and Leu42-Pro49). Helices I and II are positioned in an antiparallel mode and form one arm of the HMG box. Helix III is less rigid, makes an average angle of about 90 degrees with helices I and II, and constitutes the other arm of the molecule. As in HMG1B, the overall structure of the Sox-4 HMG box is L-shaped and is maintained by a cluster of conserved, mainly aromatic residues.

Amino Acid Sequence↗
PubMed1994

Sequence dependence of DNA structure in solution.

Sequence-dependent structural variations in DNA can influence its binding by ligands and proteins. However, relatively little is known about sequence-structure relationship for arbitrary DNA sequences. The 1H two-dimensional NOESY data presented here for ten oligonucleotide duplexes show pronounced sequence-dependent changes in at least two types of internucleotide distances commonly used in sequential connectivity assignments, namely the H-6/H-8 to preceding (5') H-1' distance (S1) and the H-6/H-8 to preceding (5') H-2'' distance (S2). On the basis of these two measured distances, all dinucleotide steps can be divided into four different groups: Y-R, R-Y, R-R and Y-Y, where R is purine and Y is pyrimidine. These data suggest some rules for the variation in these distances along DNA duplexes. Correlations between these distances and helical parameters of DNA are discussed in comparison to well-resolved X-ray structures of B-type DNA.

Base Sequence↗
PubMed1993

Structure of the complex of lac repressor headpiece and an 11 base-pair half-operator determined by nuclear magnetic resonance spectroscopy and restrained molecular dynamics.

The structure of the complex of lac repressor headpiece and an 11 base-pair lac half-operator has been determined by NMR spectroscopy and restrained Molecular Dynamics calculations. In total 508 distances were derived from two-dimensional nuclear Overhauser enhancement measurements, 260 of which are within the headpiece, 212 within the operator and 36 between operator and headpiece. An equilibrium restrained Molecular Dynamics calculation of the complex in aqueous solution, spanning 85 picoseconds, has been used to analyze the structure. Configuration sampling by an annealing procedure has been undertaken as well in order to estimate the precision of the structure determination. Our data confirm the results of previous two-dimensional NMR studies that the orientation of the recognition helix of lac repressor in the major groove of DNA with respect to the operator dyad axis is opposite to the orientation found in complexes of other DNA binding proteins of the helix-turn-helix class. We find a number of tight contacts between the protein and the operator that are in agreement with the available genetic and biochemical data. The anchoring of lac headpiece on the operator is similar to that of other repressors. Other features are unique for lac headpiece: relative few direct hydrogen bonds between side-chains and bases; extensive apolar contacts; many direct and water-bridged contacts to phosphates from residues in or close to the recognition helix. Overall, an interconnected set of interactions is observed, involving base-specific contacts, phosphate contacts, intra-protein and water-bridged hydrogen bonds. Several of these interactions appear to be dynamic, i.e. fluctuating in time, rather than static.

Amino Acid Sequence↗
PubMed1993

Investigation of solution structure of d(GAATTTAAATTC)2 by 1H NMR, molecular dynamics, mechanics, refinement by back-calculation of the NOESY spectrum and analysis of this structure using X-ray data.

1H NMR spectroscopy, restrained molecular mechanics and dynamics and refinements after back-calculation of the NOESY spectrum have been performed to study the structure of the d(GAATTTAAATTC)2 duplex and to determine whether it is bent or not. It is found that the duplex adopts a B-type conformation; all sugar conformations belong to the C2' endo region and purines have a larger pseudorotation angle as compared to pyrimidines. The cross-strand AH2(n)-AH1' (m + 1) distance (where (n) and (m) are complementary residues), crucial for an anomalous A/T tract structure, is large on the TA step and gradually decreases at the 3' and 5' ends of the TTTAAA tract and follows the rules proposed previously [Chuprina, V.P., Lipanov, A.A., Fedoroff, O.Yu, Kim, S.G., Kintanar, A., and Reid, B.R., Proc. Natl. Acad. Sci. U.S.A. 88, 9087 (1991)]. The changes in this distance correlate with those in the T1 value for AH2 protons which we measured for several oligonucleotide sequences. A total number of about 250 interproton distance constraints were determined from NOESY spectra and were used for structure determination by molecular mechanics, dynamics and refinement by back-calculations. It is shown that these data are not enough to determine whether the duplex is bent or not. The whole family of B-type conformations including bent and straight structures fit well with the available NMR data. In principle, additional non-NMR data could be used in order to reduce the number of the allowable structures. The refinement of the structures with additional different non-NMR constraints (used as a driving force) on P-P or H1'-H1' minor groove width distances in the TA region shows a very good correlation between these distances and the angle of bending of the dodecamer. The more the minor groove width increases in the TA region the more the duplex is bent at the major groove of this region. On the other hand, there is also a very good correlation between P-P, H1'-H1' and AH2-H1' cross-strand distances as follows from analysis of X-ray B-type structures. These two correlations, together with the increased AH2-H1' cross-strand NMR distance in the TA region of the dodecamer indicate that the duplex should be characterized by a wider minor groove in the TA region and be bent in the major groove in this region.

Base Sequence↗
PubMed1993

Base dependence of B-DNA sugar conformation in solution and in the solid state.

Analysis of 1H-NOESY solution data for eight short DNA duplexes has revealed pronounced differences between the sugar conformations of purine and pyrimidine nucleotides. It was found that the H1'-H4' interproton distance is less than ca. 3.0 A in pyrimidine sugars, while in purine sugars it is more than ca. 3.0A. This difference has been analyzed by comparison with the sugar conformations of highly resolved B-DNA crystal structures and model sugar conformations. The conclusion can be drawn that the deoxyribose conformation is of the general C2'-endo type but pyrimidine sugars are characterized by smaller phase angles of pseudorotation P (90 degrees < P < 150 degrees), while purine sugars have larger P values that are greater than ca. 140 degrees (140 degrees < P < 180 degrees). There is no such clear base dependence of sugar conformation in highly resolved B-DNA crystal structures; however the similar trend can be seen as in the solution studies. Based on B-type DNA crystal structures, J-coupling constants have been calculated, and the applicability of experimental coupling measurements to the determination of sugar conformation is discussed.

Base Sequence↗
PubMed1991

Dependence of the hydration shell structure in the minor groove of the DNA double helix on the groove width as revealed by Monte Carlo simulation.

The hydration shell of several conformations of the polynucleotides poly(dA).poly(dT), poly(dA).poly(dU), and poly(dA-dI).poly(dT-dC) has been simulated using the Monte Carlo method (Metropolis sampling). Calculations have shown that the structure of the hydration shell of the minor groove greatly depends on its width. In conformations with a narrowed minor groove, the first layer of the hydration shell of this groove has only one molecule per nucleotide pair that forms H bonds with purine N3 of one pair and pyrimidine O2 of the next pair. The second layer of the hydration shell of such conformations contains molecules that form H bonds between two adjacent molecules of the first layer. The probability of formation of hydration spine is about 20% while the bridges of the first layer are formed with a probability of about 70%. In the first layer of the minor groove of the B-DNA conformation with wide minor groove there are approximately two water molecules per base pair that form H bonds with purine N3 or pyrimidine O2 and with the sugar ring oxygen of the adjacent nucleotide. The probability of simultaneous H bonding of a water molecule with N3 (or O2) and O of sugar ring is about 30%. The results of simulation suggest that hydration spine proposed for the narrowed minor groove of oligonucleotide crystals [H. R. Drew, and R. E. Dickerson (1981) Journal of Molecular Biology, Vol. 151, pp. 535-556] can be formed in fibers of poly(dA).poly(dT), poly(dA).poly(dU), and poly(dA-dI).poly(dT-dC) as well as in DNA fragments of these sequences in solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1991

Sequence effects on local DNA topology.

Nuclear Overhauser effect-derived distances between adenine H2 protons and anomeric H1' protons on the same strand or on the complementary strand are presented for several different DNA duplexes. The cross-strand (n)AH2 to (m + 1)H1' distances [designated as x, where (n) and (m) are complementary residues] vary by up to 1 A depending on the sequence. In all possible A-containing pyrimidine-purine steps (CA, TG, and TA), x is greater than 4.5 A. In GA steps, x varies within rather wide limits in the range 3.8-4.5 A, whereas in AA steps the lower limit is 3.7 A and the upper limit is approximately 4.2 A. In purine-purine steps, x is affected by at least three factors: (i) adjacent pyrimidine-purine steps at the 5' end [e.g., YRA sequences (where Y = T or C and R = G or A)], or a pyrimidine-purine step at the 3' end of the pyrimidine-pyrimidine step on the complementary strand, cause x to increase, (ii) an AT step at the 3' end of a purine-purine step (e.g., RAT) causes x to decrease, and (iii) substitution of bases at the next-nearest neighbor position leads to changes in x at GA and AA steps. The latter factor seems to be due to a cooperative effect arising from formation of the "anomalous" B' structure when the substitution produces an AnTm tract (which always produces a decrease in x). The data indicate that (n)AH2-(n + 1)H1' distances on the same strand (designated as s) are also sequence dependent. Thus on AA steps, neighboring substitutions produce the same effect on s as on the cross-strand x distances. The results lead to the ability to predict changes in AH2-H1' distances depending on the DNA sequence. By using high-resolution x-ray B-type structures as a set of allowable B conformations, a very good correlation was found between x and the minor groove width parameters P-P or H1'-H1'. Thus, the x distances are a direct probe of the minor groove width in B-type DNA, and changes in this distance therefore reflect changes in the minor groove width. Since many of the sequences studied are sites of protein recognition, the observed sequence-structure dependence in DNA probably plays an important role in the process of recognition by proteins and minor groove ligands such as drugs.

Base Sequence↗
PubMed1991

New insights into the structure of An tracts and B'-B' bends in DNA.

Energy calculations suggest that the currently available NOE distance constraints for An tracts in DNA are incapable of distinguishing between structures with a narrowed minor groove arising from a large propeller twist with a small inclination or from a small propeller twist with a large negative inclination. Furthermore, analysis of published data, together with energy estimations, strongly argue against bifurcated hydrogen bonding between A and T residues being the cause of the anomalous structural properties of An tracts. A conformational analysis of the B'-B' junction has been performed in which a single variable base pair has been inserted between two regions of B' structure. We have calculated low-energy structures for AnGAn,AnCAn,AnTAn,AnCTn, and TnCAn duplexes, where the An and Tn tracts were fixed in the anomalous B' conformation. Upon optimization, all these structures were found to contain a pronounced roll-like bending into the major groove at the site of the insertion. The important factors in the formation of these B'-B' bends are the destruction of the B' conformation and the concomitant widening of the minor groove at the junction region in order to reduce minor groove interstrand base clashes and improve interstrand stacking energy. If the B' conformation has strong negative inclination, the improved intrastrand stacking energy also contributes to the bending. In calculations of duplexes with An and Tn tracts in the B conformation instead of B', the bending disappears.

Base Sequence↗
PubMed1991

Molecular dynamics simulation of the hydration shell of a B-DNA decamer reveals two main types of minor-groove hydration depending on groove width.

The conformation of the self-complementary B-DNA decamer C-C-A-A-C-G-T-T-G-G is known from a high-resolution x-ray crystal structure analysis. Molecular dynamics simulation of the hydration shell of the decamer has revealed two main types of minor-groove hydration, depending on groove width. The narrow part of the minor groove has a spine of hydration analogous to that described for the A + T-rich center of the minor groove in the dodecamer C-G-C-G-A-A-T-T-C-G-C-G [Drew, H. R. & Dickerson, R. E. (1981) J. Mol. Biol. 151, 535-556], the first hydration layer of which contains one water molecular per base pair. In contrast, in the wide part of the minor groove, each base is hydrated individually, water molecules lying predominantly in the base plane. In intermediate-width regions, preferred water-molecule sites are shifted away from the base plane in a 3'-to-5' direction. This shift becomes more pronounced as the minor groove narrows, until the two water molecules lie approximately midway between base pairs. If the minor groove is narrowed still further, it accommodates only one water molecule, and the hydration transforms to the well-known water spine. The observed pattern agrees with available crystallographic data and with our earlier calculations. The results confirm the assumption that preferred positions of water oxygens in the minor groove depend predominantly on groove width rather than on base sequence. However, the location of water hydrogens, and the network of hydrogen bonding, can depend on base sequence. We suggest a simple explanation of water-spine formation in the narrow minor groove of a random DNA sequence. The spine of hydration may be a property of the minor groove of overwound variants of B-DNA, the C and D forms, for which the middle part of the decamer C-C-A-A-C-G-T-T-G-G can serve as a model.

Base Sequence↗
PubMed1990

Electrophoretic behavior of d(GGAAAAAAGG)n, d(CCAAAAAACC)n, and (CCAAAAAAGG)n and implications for a DNA bending model.

Double stranded multimers (C2A6C2)n, (C2A6G2)n and (G2A6G2)n were prepared from chemically synthesized oligonucleotides to study the influence of sequences flanking the An tract on the curvature of DNA. All these duplexes, including polypurine.polypyrimidine one, exhibit strong retardation in polyacrylamide gel which is indicative of pronounced DNA curvature. It has been proposed previously that among the bends at the boundary with the oligo(A) tract two types should be distinguished: 5'-bends and 3'-bends (Koo et al., 1986) This distinction was deduced from different relative mobilities of two specially designed sequences having phased 5'-bends and 3'-bends, respectively. Our data indicate that the substitutions of nucleotides at both 5' and 3' boundaries of A6 tract result in comparable changes in relative mobility. Therefore, for B-B' bends it is important to take into account not only whether they are at the 5' or 3' end of an oligo(dA) tract, but also the particular sequences at the boundaries of this tract.

Base Sequence↗
PubMed1990

Bh-DNA: variations of the poly[d(A)].poly[d(T)] structure within the framework of the fibre diffraction studies.

A refinement of the recent results for poly[d(A)].poly[d(T)] (Alexeev et al., J. Biomol. Struct. Dyn. 4,989 (1987)) involving additional parameters of the base-pair structure and of the sugar-phosphate backbone expands the conformational potential of this polynucleotide of the B type to include the possibility of bifurcated hydrogen bonds of the kind recently discovered in crystalline deoxyoligonucleotide with lone d(A)n.d(T)n stretch (Nelson et al., Nature 330, 221 (1987)). Still, analysis of the available data and energy calculations do not seem to indicate that the bifurcated H-bonds are a crucial factor responsible for the anomalous structure of the d(A)n.d(T)n sequence. The unique structural properties of poly[d(A)].poly[d(T)] can hardly be explained without taking into account its interactions with the double-layer hydration spine in the minor groove. In view of the hydration mechanism stabilizing poly[d(A)].poly[d(T)] and of the polynucleotide's heteronomous prehistory (Arnott et al., Nucleic Acids Res. 11,4141 (1983)) we suggest that this B-type structure be called Bh.

Base Composition↗
PubMed1989

DNA B to D transition can be explained in terms of hydration economy of the minor groove atoms.

Adjacent phosphate oxygen atoms in A and Z-DNA are located much closer together than in the B form and can be hydrated more economically due to the formation of water bridges between them, whereas in the B form phosphates are hydrated individually. This principle of hydration economy of phosphate groups discovered by Saenger and colleagues could not be applied to the B-D transition, which, like the B-A and B-Z transitions, occurs in a situation of water deficiency, because the distances between adjacent phosphates of individual polynucleotide chains in the D form are not much different from B-DNA. It follows from our calculations of B and D-DNA accessibility to solvent performed by the method of Lee & Richards, and from a simulation of solvent structure near DNA, that there is an economy of hydration only for the minor groove atoms. This feature and some experimental data can explain why only a limited range of sequences consisting of A.T or I.C pairs undergo the transition to the D form. The conformational transition in DNAs with such sequences to a poly[d(A]).poly[d(T])-like conformation (Bh-DNA), which is accompanied by a narrowing of the minor groove, can be explained in the same way. Calculations suggest that in the D-form minor groove of different A-T or I-C DNAs there is a double-layer hydration spine similar to that observed by Drew & Dickerson in the A-T tract of the d(C-G-C-G-A-A-T-T-C-G-C-G) dodecamer. The B-D and B-Bh transitions in A + T-rich DNAs can have biological implications, e.g. they can facilitate DNA bending upon the interaction with proteins.

DNA↗
PubMed1989

Measurement of anomalously high hydration of (dA)n.(dT)n double helices in dilute solution.

Different DNA sequences have different physical properties, which seem to be important for their biological function. In particular, (dA)n.(dT)n has many unusual features, which include resistance to conformational changes in a variable chemical environment, an unusual thermodynamics of interaction with ligands, and the inability to reassociate into nucleosomes. Short A.T base-pair runs also play a critical role in DNA bending. It is believed that hydration of DNA is an important factor in determining the physical chemical and biological properties of different regions of DNA. Until now, however, it has not been possible to study the details of the hydration of DNA in dilute solution with sufficient sensitivity and precision. Moreover, it was not known if different base sequences differ in the extent of their hydration. Indirect evidence that (dA)n.(dT)n can be hydrated to a greater extent than other DNA sequences may be inferred from a recent study of the binding of drugs to polynucleotides. Here we used a novel high-precision technique measuring ultrasonic velocity to obtain direct estimates of the extent of hydration of various oligo- and polynucleotides in dilute solution. We report that different DNA sequences differ in their hydration, and that (dA)n.(dT)n in particular has an anomalously high level of hydration.

Base Sequence↗
PubMed1989

Critical comments on the one recent DNA bending model and its fit to electrophoretic data.

The approach of Calladine, Drew and McCall (J. Mol. Biol 201, 127-137, 1988) for the investigation of DNA curvature has been analyzed. The authors relate their bending parameters to the experimental data on the basis of a new method of predicting electrophoretic anomalies from the trajectory of helical axis. This method of treating the DNA superhelix as a rigid body seems to be hardly applicable to the cases when superhelical turn is longer than or comparable to persistence length of straight DNA (approximately 150 bp). The extrapolation of experimental curves to plateau, done in a number of cases, seems somewhat arbitrary. Besides, alternative angle sets (e.g., with the roll angle on the AA step not equal to zero) having the same or even better fit to experimental data can be found even within the framework of the proposed approach. Another serious drawback of the model is its inability to account for new data (H.-S. Koo and D.M. Crothers. PNAS 85, 1763-1767, 1988), the predicted values of relative anomaly on (N8A6N5A6N4A6N7) multimers amounting to thousands.

DNA↗