scholarly journals How does Mg2+ modulate the RNA folding mechanism — a case study of G:C W:W Trans base pair

2017 ◽  
Author(s):  
Antarip Halder ◽  
Rohit Roy ◽  
Dhananjay Bhattacharyya ◽  
Abhijit Mitra
Keyword(s):  
Crystal Structures ◽  
Base Pair ◽  
Rna Structure ◽  
Binding Modes ◽  
Base Pairs ◽  
Bonding Interaction ◽  
Direct Binding ◽  
And Function ◽  
Experimental Geometry

AbstractReverse Watson-Crick G:C base pairs (G:C W:W Trans) occur frequently in different functional RNAs. It is one of the few base pairs whose gas phase optimized isolated geometry is inconsistent with the corresponding experimental geometry. Several earlier studies indicate that accumulation of positive charge near N7 of guanine, through posttranscriptional modification, direct protonation or coordination with Mg2+, can stabilize the experimental geometry. Interestingly, recent studies reveal significant variation in the position of putatively bound Mg2+. This, in conjunction with recently raised doubts regarding some of the Mg2+ assignments near the imino nitrogen of guanine, is suggestive of the existence of multiple Mg2+ binding modes for this base pair. Our detailed investigation of Mg2+ bound G:C W:W Trans pairs, occurring in high resolution RNA crystal structures, show that they occur in 14 different contexts, 8 out of which display Mg2+ binding at the Hoogsteen edge of guanine. Further examination of occurrences in these 8 contexts led to the characterization of three different Mg2+ binding modes, (i) direct binding via N7 coordination, (ii) direct binding via O6 coordination and (iii) binding via hydrogen bonding interaction with the first shell water molecules. In the crystal structures, the latter two modes are associated with a buckled and propeller twisted geometry of the base pair. Interestingly, respective optimized geometries of these different Mg2+ binding modes (optimized at B3LYP) are consistent with their corresponding experimental geometries. Subsequent interaction energy calculations at MP2 level, and decomposition of its components, suggest that for G:C W:W Trans, Mg2+ binding can fine tune the base pair geometries without compromising with their stability. Our results, therefore, underline the importance of the mode of binding of Mg2+ ions in shaping RNA structure, folding and function.

Three-centre C—H...O hydrogen bonds in the DNA minor groove: analysis of oligonucleotide crystal structures

1999 ◽  
Vol 55 (12) ◽  
pp. 2005-2012 ◽  
Author(s):  
Anirban Ghosh ◽  
Manju Bansal
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Base Pair ◽  
Minor Groove ◽  
Local Geometry ◽  
Data Sets ◽  
Base Pairs ◽  
Dna Minor Groove ◽  
Close Proximity ◽  
Using Data

AA·TT and GA·TC dinucleotide steps in B-DNA-type oligomeric crystal structures and in protein-bound DNA fragments (solved using data with resolution <2.6 Å) show very small variations in their local dinucleotide geometries. A detailed analysis of these crystal structures reveals that in AA·TT and GA·TC steps the electropositive C2—H2 group of adenine is in very close proximity to the keto O atoms of both the pyrimidine bases in the antiparallel strand of the duplex structure, suggesting the possibility of intra-base pair as well as cross-strand inter-base pair C—H...O hydrogen bonds in the DNA minor groove. The C2—H2...O2 hydrogen bonds in the A·T base pairs could be a natural consequence of Watson–Crick pairing. However, the cross-strand interactions between the bases at the 3′-end of the AA·TT and GA·TC steps obviously arise owing to specific local geometry of these steps, since a majority of the H2...O2 distances in both data sets are considerably shorter than their values in the uniform fibre model (3.3 Å) and many are even smaller than the sum of the van der Waals radii. The analysis suggests that in addition to already documented features such as the large propeller twist of A·T base pairs and the hydration of the minor groove, these C2—H2...O2 cross-strand interactions may also play a role in the narrowing of the minor groove in A-tract regions of DNA and help explain the high structural rigidity and stability observed for poly(dA)·poly(dT).

scholarly journals Frequency and hydrogen bonding of nucleobase homopairs in small molecule crystals

2020 ◽  
Vol 48 (15) ◽  
pp. 8302-8319
Author(s):  
Małgorzata Katarzyna Cabaj ◽  
Paulina Maria Dominiak
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Small Molecule ◽  
Base Pair ◽  
Base Pairs ◽  
Standard Pattern ◽  
Planar Structures ◽  
Structural Database ◽  
Derivatives Of

Abstract We used the high resolution and accuracy of the Cambridge Structural Database (CSD) to provide detailed information regarding base pairing interactions of selected nucleobases. We searched for base pairs in which nucleobases interact with each other through two or more hydrogen bonds and form more or less planar structures. The investigated compounds were either free forms or derivatives of adenine, guanine, hypoxanthine, thymine, uracil and cytosine. We divided our findings into categories including types of pairs, protonation patterns and whether they are formed by free bases or substituted ones. We found base pair types that are exclusive to small molecule crystal structures, some that can be found only in RNA containing crystal structures and many that are native to both environments. With a few exceptions, nucleobase protonation generally followed a standard pattern governed by pKa values. The lengths of hydrogen bonds did not depend on whether the nucleobases forming a base pair were charged or not. The reasons why particular nucleobases formed base pairs in a certain way varied significantly.

Covalent Analogues of DNA Base-Pairs and Triplets V. Synthesis of Purine-Purine and Purine-Pyrimidine Conjugates Connected by Diverse Types of Acyclic Carbon Linkages

2002 ◽  
Vol 67 (10) ◽  
pp. 1560-1578 ◽  
Author(s):  
Michal Hocek ◽  
Hana Dvořáková ◽  
Ivana Císařová
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Base Pair ◽  
Cross Coupling ◽  
X Ray Diffraction ◽  
Base Pairs ◽  
X Ray ◽  
Dna Base ◽  
Dna Base Pairs ◽  
Purine Pyrimidine

The title 1,2-bis(purin-6-yl)acetylenes, -diacetylenes, -ethylenes and -ethanes were prepared as covalent base-pair analogues starting from 6-ethynylpurines and 6-iodopurines by the Sonogashira cross-coupling or oxidative alkyne-dimerization reactions followed by hydrogenations. 6-[(1,3-Dimethyluracil-5-yl)ethynyl]purine (11) was prepared analogously and hydrogenated to the corresponding purine-pyrimidine conjugates linked via vinylene and ethylene linkers. Unlike the cytostatic bis(purin-6-yl)acetylenes and -diacetylenes, the purine-pyrimidine conjugates were inactive. Crystal structures of bis(purin-6-yl)acetylene 6a, -diacetylene 8a and -ethane 5a were determined by single-crystal X-ray diffraction.

scholarly journals Symmetry in Nucleic-Acid Double Helices

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 737
Author(s):  
Udo Heinemann ◽  
Yvette Roske
Keyword(s):  
Nucleic Acid ◽  
Base Pair ◽  
Rna Structure ◽  
Test Tube ◽  
Base Pairs ◽  
Dna And Rna ◽  
Left Handed ◽  
Double Helices ◽  
Rna Duplexes ◽  
The Right

In nature and in the test tube, nucleic acids occur in many different forms. Apart from single-stranded, coiled molecules, DNA and RNA prefer to form helical arrangements, in which the bases are stacked to shield their hydrophobic surfaces and expose their polar edges. Focusing on double helices, we describe the crucial role played by symmetry in shaping DNA and RNA structure. The base pairs in nucleic-acid double helices display rotational pseudo-symmetry. In the Watson–Crick base pairs found in naturally occurring DNA and RNA duplexes, the symmetry axis lies in the base-pair plane, giving rise to two different helical grooves. In contrast, anti-Watson–Crick base pairs have a dyad axis perpendicular to the base-pair plane and identical grooves. In combination with the base-pair symmetry, the syn/anti conformation of paired nucleotides determines the parallel or antiparallel strand orientation of double helices. DNA and RNA duplexes in nature are exclusively antiparallel. Watson–Crick base-paired DNA or RNA helices display either right-handed or left-handed helical (pseudo-) symmetry. Genomic DNA is usually in the right-handed B-form, and RNA double helices adopt the right-handed A-conformation. Finally, there is a higher level of helical symmetry in superhelical DNA in which B-form double strands are intertwined in a right- or left-handed sense.

Fluorescent ribonucleoside analogues as probes for investigating RNA structure and function

2010 ◽  
Vol 83 (1) ◽  
pp. 213-232 ◽  
Author(s):  
Seergazhi G. Srivatsan ◽  
Anupam A. Sawant
Keyword(s):  
Nucleic Acid ◽  
Conformational Changes ◽  
Rna Structure ◽  
Photophysical Properties ◽  
Local Environment ◽  
Spectroscopic Techniques ◽  
Rna Structures ◽  
Base Pairs ◽  
Target Nucleic Acid ◽  
And Function

Numerous biophysical tools based on fluorescence have been developed to advance the understanding of RNA–nucleic acid, RNA–protein, and RNA–small molecule inter-actions. In this regard, fluorescent ribonucleoside analogues that are sensitive to their local environment provide sensitive probes for investigating RNA structure, dynamics, and recognition. Most of these analogues closely resemble the native ribonucleosides with respect to their overall dimension and have the ability to form canonical Watson–Crick (WC) base pairs. Therefore, it is possible to place these probes near the point of interaction in a target nucleic acid with minimum structural perturbations and gain insight into the intricacies of conformational changes taking place in and around the interaction site. Here, we provide a concise background on the development and recent advances in the applications of base-modified fluorescent ribonucleoside analogue probes. We first present various base-modified fluorescent ribonucleoside analogues, their photophysical properties, and methods to incorporate these analogues into oligoribonucleotides. We then discuss the established spectroscopic techniques, which make use of the fluorescence properties of these emissive ribonucleoside analogues. Finally, we present the applications of base-modified fluorescent ribonucleoside analogues used as probes incorporated into oligoribonucleotides in investigating RNA structures and functions.

scholarly journals Simultaneous characterization of cellular RNA structure and function with in-cell SHAPE-Seq

2015 ◽  
Vol 44 (2) ◽  
pp. e12-e12 ◽  
Author(s):  
Kyle E. Watters ◽  
Timothy R. Abbott ◽  
Julius B. Lucks
Keyword(s):  
Rna Structure ◽  
Cell Shape ◽  
Structure And Function ◽  
And Function

scholarly journals Response to Tavares et al., “Covariation analysis with improved parameters reveals conservation in lncRNA structures”

2020 ◽  
Author(s):  
Elena Rivas ◽  
Sean R. Eddy
Keyword(s):  
Base Pair ◽  
Rna Structure ◽  
Negative Control ◽  
Sequence Conservation ◽  
Primary Sequence ◽  
Base Pairs ◽  
Sequence Alignments ◽  
Evolutionarily Conserved ◽  
Conservation Patterns ◽  
Covariation Analysis

AbstractTavares’ conclusions depend on an assumption that the statistic they use (RAFS) is an appropriate measure of RNA base pair covariation, but RAFS was not designed to measure covariation alone. RAFS detects positive signals in common patterns of primary sequence conservation in absence of any covariation. To illustrate the severity of the problem, we show that Tavares’ analysis reports “significantly covarying base pairs” in 100% identical sequence alignments with no variation or covariation. We use Tavares’ sequence alignment of HOTAIR domain 1 as an example to show that the base pairs they identify as significantly covarying actually arise from primary sequence conservation patterns. Their analysis still reports similar numbers of “significant covarying” base pairs in a negative control in which we permute residues in independent alignment columns to destroy covariation. There remains no significant covariation support for evolutionarily conserved RNA structure in the HOTAIR lncRNA or other lncRNA structures and alignments we have analyzed.

Functional characterization of human brown adipose tissue metabolism

2020 ◽  
Vol 477 (7) ◽  
pp. 1261-1286 ◽  
Author(s):  
Marie Anne Richard ◽  
Hannah Pallubinsky ◽  
Denis P. Blondin
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Functional Characterization ◽  
Human Infants ◽  
Positron Emission ◽  
Brown Adipose ◽  
Treatment Of Obesity ◽  
And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

Parasite defense mechanisms in bees: behavior, immunity, antimicrobials, and symbionts

2019 ◽  
Vol 4 (1) ◽  
pp. 59-76 ◽  
Author(s):  
Alison E. Fowler ◽  
Rebecca E. Irwin ◽  
Lynn S. Adler
Keyword(s):  
Defense Mechanisms ◽  
Poor Quality ◽  
Future Research ◽  
Immune Priming ◽  
Social Bees ◽  
Bee Health ◽  
Landscape Scales ◽  
And Function ◽  
Solitary Species

Parasites are linked to the decline of some bee populations; thus, understanding defense mechanisms has important implications for bee health. Recent advances have improved our understanding of factors mediating bee health ranging from molecular to landscape scales, but often as disparate literatures. Here, we bring together these fields and summarize our current understanding of bee defense mechanisms including immunity, immunization, and transgenerational immune priming in social and solitary species. Additionally, the characterization of microbial diversity and function in some bee taxa has shed light on the importance of microbes for bee health, but we lack information that links microbial communities to parasite infection in most bee species. Studies are beginning to identify how bee defense mechanisms are affected by stressors such as poor-quality diets and pesticides, but further research on this topic is needed. We discuss how integrating research on host traits, microbial partners, and nutrition, as well as improving our knowledge base on wild and semi-social bees, will help inform future research, conservation efforts, and management.

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