scholarly journals ADAR-Independent A-to-I RNA Editing is Generally Adaptive for Sexual Reproduction in Fungi

2016 ◽  
Author(s):  
Qinhu Wang ◽  
Cong Jiang ◽  
Huiquan Liu ◽  
Jin-Rong Xu
Keyword(s):  
Amino Acid ◽  
Sexual Reproduction ◽  
Rna Editing ◽  
Protein Structures ◽  
Biological Significance ◽  
Chemical Properties ◽  
Rna Modification ◽  
Amino Acid Substitutions ◽  
Protein Functions ◽  
Conserved Genes

ABSTRACTADAR-mediated A-to-I RNA editing is a well-known RNA modification mechanism in metazoans that can cause nonsynonymous changes leading to amino acid substitutions. Despite a few cases that are clearly functionally important, the biological significance of most nonsynonymous editing sites in animals remains largely unknown. Recently, genome-wide A-to-I editing was found to occur mainly in the coding regions and specifically during sexual reproduction in the wheat scab fungus Fusarium graminearum that lacks ADAR orthologs. In this study, we found that both the frequency and editing level of nonsynonymous editing is significantly higher than those of synonymous editing, suggesting that nonsynonymous editing is generally beneficial and under positive selection in F. graminearum. We also showed that nonsynonymous editing favorably targets functionally more important and more conserved genes, but at less-conserved sites, indicating that the RNA editing system is adapted to fine turn protein functions by avoiding potentially deleterious editing events. Furthermore, nonsynonymous editing in F. graminearum was found to be under codon-specific selection and most types of codon changes tend to cause amino acid substitutions with distinct physical-chemical properties and smaller molecular weights, which likely have more profound impact on protein structures and functions. In addition, we found that the most abundant synonymous editing of leucine codons is adapted to fine turn the protein expression by increasing codon usage bias. These results clearly show that A-to-I RNA editing in fungi is generally adaptive and recoding RNA editing may play an important role in sexual development in filamentous ascomycetes.

scholarly journals Evolutionary Analyses of RNA Editing and Amino Acid Recoding in Cephalopods

2019 ◽  
Author(s):  
Mingye (Christina) Wang ◽  
Erik Mohlhenrich
Keyword(s):  
Amino Acid ◽  
Candidate Genes ◽  
Rna Editing ◽  
Amino Acid Level ◽  
Nucleotide Composition ◽  
Model Organisms ◽  
Future Research ◽  
Amino Acid Substitutions ◽  
Behavioral Complexity ◽  
Fitness Advantage

AbstractRNA editing is a post-transcriptional modification process that alters nucleotides of mRNA and consequently the amino acids of the translated protein without changing the original DNA sequence. In human and other mammals, amino acid recoding from RNA editing is rare, and most edits are non-adaptive and provide no fitness advantage (1). However, recently it was discovered that in soft-bodied cephalopods, which are exceptionally intelligent and include squid, octopus, and cuttlefish, RNA editing is widespread and positively selected (2). To examine the effects of RNA editing on individual genes, we developed a “diversity score” system that quantitatively assesses the amount of diversity generated in each gene, incorporating combinatorial diversity and the radicalness of amino acid changes. Using this metric, we compiled a list of top 100 genes across the cephalopod species that are most diversified by RNA editing. This list of candidate genes provides directions for future research into the specific functional impact of RNA editing in terms of protein structure and cellular function on individual proteins. Additionally, considering the connection of RNA editing to the nervous system, and the exceptional intelligence of cephalopod, the candidate genes may shed light to the molecular development of behavioral complexity and intelligence. To further investigate global influences of RNA editing on the transcriptome, we investigated changes in nucleotide composition and codon usage biases in edited genes and coleoid transcriptome in general. Results show that these features indeed correlate with editing and may correspond to causes or effects of RNA editing. In addition, we characterized the unusual RNA editing in cephalopods by analyzing ratio of radical to conservative amino acid substitutions (R/C) and distribution of amino acid recoding from editing. Our results show that compared to model organisms, editing in cephalopods have significantly decreased R/C ratio and distinct distribution of amino acid substitutions that favor conservative over radical changes, indicating selection at the amino acid level and providing a potential mechanism for the evolution of widespread RNA editing in cephalopods.

scholarly journals Multiple substitutions lead to increased loop flexibility and expanded specificity in Acinetobacter baumannii carbapenemase OXA-239

2018 ◽  
Vol 475 (1) ◽  
pp. 273-288 ◽  
Author(s):  
Thomas M. Harper ◽  
Cynthia M. June ◽  
Magdalena A. Taracila ◽  
Robert A. Bonomo ◽  
Rachel A. Powers ◽  
...  
Keyword(s):  
Amino Acid ◽  
Acinetobacter Baumannii ◽  
Active Site ◽  
Active Sites ◽  
Protein Structures ◽  
Amino Acid Substitutions ◽  
The Third ◽  
Class D ◽  
Late Generation ◽  
Loop Flexibility

OXA-239 is a class D carbapenemase isolated from an Acinetobacter baumannii strain found in Mexico. This enzyme is a variant of OXA-23 with three amino acid substitutions in or near the active site. These substitutions cause OXA-239 to hydrolyze late-generation cephalosporins and the monobactam aztreonam with greater efficiency than OXA-23. OXA-239 activity against the carbapenems doripenem and imipenem is reduced ∼3-fold and 20-fold, respectively. Further analysis demonstrated that two of the substitutions (P225S and D222N) are largely responsible for the observed alteration of kinetic parameters, while the third (S109L) may serve to stabilize the protein. Structures of OXA-239 with cefotaxime, doripenem and imipenem bound as acyl-intermediates were determined. These structures reveal that OXA-239 has increased flexibility in a loop that contains P225S and D222N. When carbapenems are bound, the conformation of this loop is essentially identical with that observed previously for OXA-23, with a narrow active site that makes extensive contacts to the ligand. When cefotaxime is bound, the loop can adopt a different conformation that widens the active site to allow binding of that bulky drug. This alternate conformation is made possible by P225S and further stabilized by D222N. Taken together, these results suggest that the three substitutions were selected to expand the substrate specificity profile of OXA-23 to cephalosporins and monobactams. The loss of activity against imipenem, however, suggests that there may be limits to the plasticity of class D enzymes with regard to evolving active sites that can effectively bind multiple classes of β-lactam drugs.

scholarly journals Human C-to-U Coding RNA Editing Is Largely Nonadaptive

2018 ◽  
Vol 35 (4) ◽  
pp. 963-969 ◽  
Author(s):  
Zhen Liu ◽  
Jianzhi Zhang
Keyword(s):  
Rna Editing ◽  
Protein Function ◽  
Biological Significance ◽  
Rna Modification ◽  
Rna Molecules ◽  
Median Proportion ◽  
Specific Regulation ◽  
Time Specific ◽  
A Site ◽  
Editing Level

Abstract C-to-U RNA editing enzymatically converts the base C to U in RNA molecules and could lead to nonsynonymous changes when occurring in coding regions. Hundreds to thousands of coding sites were recently found to be C-to-U edited or editable in humans, but the biological significance of this phenomenon is elusive. Here, we test the prevailing hypothesis that nonsynonymous editing is beneficial because it provides a means for tissue- or time-specific regulation of protein function that may be hard to accomplish by mutations due to pleiotropy. The adaptive hypothesis predicts that the fraction of sites edited and the median proportion of RNA molecules edited (i.e., editing level) are both higher for nonsynonymous than synonymous editing. However, our empirical observations are opposite to these predictions. Furthermore, the frequency of nonsynonymous editing, relative to that of synonymous editing, declines as genes become functionally more important or evolutionarily more constrained, and the nonsynonymous editing level at a site is negatively correlated with the evolutionary conservation of the site. Together, these findings refute the adaptive hypothesis; they instead indicate that the reported C-to-U coding RNA editing is mostly slightly deleterious or neutral, probably resulting from off-target activities of editing enzymes. Along with similar conclusions on the more prevalent A-to-I editing and m6A modification of coding RNAs, our study suggests that, at least in humans, most events of each type of posttranscriptional coding RNA modification likely manifest cellular errors rather than adaptations, demanding a paradigm shift in the research of posttranscriptional modification.

scholarly journals Evolutionary model of protein secondary structure capable of revealing new biological relationships

2019 ◽  
Author(s):  
Jhih-Siang Lai ◽  
Burkhard Rost ◽  
Bostjan Kobe ◽  
Mikael Bodén
Keyword(s):  
Amino Acid ◽  
Secondary Structure ◽  
Predictive Accuracy ◽  
Protein Structures ◽  
Protein Secondary Structure ◽  
Evolutionary Model ◽  
Ancestral Sequences ◽  
Recent Success ◽  
Protein Functions ◽  
Sequence Reconstruction

AbstractAncestral sequence reconstruction has had recent success in decoding the origins and the determinants of complex protein functions. However, phylo­genetic analyses of remote homologues must handle extreme amino-acid se­quence diversity resulting from extended periods of evolutionary change. We exploited the wealth of protein structures to develop an evolutionary model based on protein secondary structure. The approach follows the differences between discrete secondary structure states observed in modern proteins and those hypothesised in their immediate ancestors. We implemented maximum likelihood-based phylogenetic inference to reconstruct ancestral secondary structure. The predictive accuracy from the use of the evolutionary model surpasses that of comparative modelling and sequence-based prediction; the reconstruction extracts information not available from modern structures or the ancestral sequences alone. Based on a phylogenetic analysis of multiple protein families, we showed that the model can highlight relationships that are evolutionarily rooted in structure and not evident in amino acid-based analysis.

scholarly journals A little walk from physical to biological complexity: protein folding and stability

2016 ◽  
Author(s):  
Fabrizio Pucci ◽  
Marianne Rooman
Keyword(s):  
Protein Folding ◽  
Amino Acid ◽  
Thermal Resistance ◽  
Protein Structures ◽  
Amino Acid Substitutions ◽  
Biological Complexity ◽  
Statistical Potentials ◽  
Bioinformatics Tools ◽  
The Stability ◽  
Boltzmann Law

As an example of topic where biology and physics meet, we present the issue of protein folding and stability, and the development of thermodynamics-based bioinformatics tools that predict the stability and thermal resistance of proteins and the change of these quantities upon amino acid substitutions. These methods are based on knowledge-driven statistical potentials, derived from experimental protein structures using the inverse Boltzmann law.

scholarly journals Evolutionary Models of Amino Acid Substitutions Based on the Tertiary Structure of their Neighborhoods

2018 ◽  
Author(s):  
Elias Primetis ◽  
Spyridon Chavlis ◽  
Pavlos Pavlidis
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Substitution ◽  
Tertiary Structure ◽  
Protein Structures ◽  
Amino Acid Substitutions ◽  
Tertiary Structures ◽  
Substitution Matrices ◽  
Amino Acid Substitution Model ◽  
Amino Acid Substitution Matrices

AbstractIntra-protein residual vicinities depend on the involved amino acids. Energetically favorable vicinities (or interactions) have been preserved during evolution, while unfavorable vicinities have been eliminated. We describe, statistically, the interactions between amino acids using resolved protein structures. Based on the frequency of amino acid interactions, we have devised an amino acid substitution model that implements the following idea: amino acids that have similar neighbors in the protein tertiary structure can replace each other, while substitution is more difficult between amino acids that prefer different spatial neighbors. Using known tertiary structures for α-helical membrane (HM) proteins, we build evolutionary substitution matrices. We constructed maximum likelihood phylogenies using our amino acid substitution matrices and compared them to widely-used methods. Our results suggest that amino acid substitutions are associated with the spatial neighborhoods of amino acid residuals, providing, therefore, insights into the amino acid substitution process.

scholarly journals Amino acid torsion angles enable prediction of protein fold classification

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Kun Tian ◽  
Xin Zhao ◽  
Xiaogeng Wan ◽  
Stephen S.-T. Yau
Keyword(s):  
Protein Structure ◽  
Amino Acid ◽  
Protein Structure Prediction ◽  
Structure Prediction ◽  
High Throughput Sequencing ◽  
Protein Structures ◽  
Amino Acid Sequences ◽  
Single Amino Acid ◽  
New Approach ◽  
Protein Functions

AbstractProtein structure can provide insights that help biologists to predict and understand protein functions and interactions. However, the number of known protein structures has not kept pace with the number of protein sequences determined by high-throughput sequencing. Current techniques used to determine the structure of proteins are complex and require a lot of time to analyze the experimental results, especially for large protein molecules. The limitations of these methods have motivated us to create a new approach for protein structure prediction. Here we describe a new approach to predict of protein structures and structure classes from amino acid sequences. Our prediction model performs well in comparison with previous methods when applied to the structural classification of two CATH datasets with more than 5000 protein domains. The average accuracy is 92.5% for structure classification, which is higher than that of previous research. We also used our model to predict four known protein structures with a single amino acid sequence, while many other existing methods could only obtain one possible structure for a given sequence. The results show that our method provides a new effective and reliable tool for protein structure prediction research.

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