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Choanoflagellates are single-celled eukaryotes with complex signaling pathways. They are considered the closest non-metazoan ancestors to mammals and other metazoans and form multicellular-like states called rosettes. The choanoflagellate Monosiga brevicollis contains over 150 PDZ domains, an important peptide-binding domain in all three domains of life (Archaea, Bacteria, and Eukarya). Therefore, an understanding of PDZ domain signaling pathways in choanoflagellates may provide insight into the origins of multicellularity. PDZ domains recognize the C-terminus of target proteins and regulate signaling and trafficking pathways, as well as cellular adhesion. Here, we developed a computational software suite, Domain Analysis and Motif Matcher (DAMM), that analyzes peptide-binding cleft sequence identity as compared with human PDZ domains and that can be used in combination with literature searches of known human PDZ-interacting sequences to predict target specificity in choanoflagellate PDZ domains. We used this program, protein biochemistry, fluorescence polarization, and structural analyses to characterize the specificity of A9UPE9_MONBE, a M. brevicollis PDZ domain-containing protein with no homology to any metazoan protein, finding that its PDZ domain is most similar to those of the DLG family. We then identified two endogenous sequences that bind A9UPE9 PDZ with &lt, 100 μM affinity, a value commonly considered the threshold for cellular PDZ–peptide interactions. Taken together, this approach can be used to predict cellular targets of previously uncharacterized PDZ domains in choanoflagellates and other organisms. Our data contribute to investigations into choanoflagellate signaling and how it informs metazoan evolution.

Choanoflagellates are single-celled eukaryotes with complex signaling pathways. They are considered the closest non-metazoan ancestors to mammals and other metazoans and form multicellular-like states called rosettes. The choanoflagellate Monosiga brevicollis contains over 150 PDZ domains, an important peptide-binding domain in all three domains of life (Archaea, Bacteria, and Eukarya). Therefore, an understanding of PDZ domain signaling pathways in choanoflagellates may provide insight into the origins of multicellularity. PDZ domains recognize the C-terminus of target proteins and regulate signaling and trafficking pathways, as well as cellular adhesion. Here, we developed a computational software suite, Domain Analysis and Motif Matcher (DAMM), that analyzes peptide-binding cleft sequence identity as compared with human PDZ domains and that can be used in combination with literature searches of known human PDZ-interacting sequences to predict target specificity in choanoflagellate PDZ domains. We used this program, protein biochemistry, fluorescence polarization, and structural analyses to characterize the specificity of A9UPE9_MONBE, a M. brevicollis PDZ domain-containing protein with no homology to any metazoan protein, finding that its PDZ domain is most similar to those of the DLG family. We then identified two endogenous sequences that bind A9UPE9 PDZ with

Scientific workflows often consist of black-box stand-alone programs that each write to one or more files, resulting in significant I/O operations. When strung together, each stage of the pipeline is bottlenecked by I/O, without much ability to modify that behavior. Since computation capabilities of large-scale distributed systems grow much faster than their I/O bandwidth, processing such big data using these workflows does not scale as the amount of data grows. While most related work focuses on data aggregation by modifying source code, we propose a Function Interception Library for Collective I/O (FILCIO), to intercept I/O function calls in C’s stdio library on a POSIX file system. This aggregates outgoing data in memory before writing to disk. Our aim is to scale I/O intensive scientific workflows without needing to access and modify their source code. In this paper, we motivate the need for I/O aggregation, and discuss what applications are poised to benefit most from FILCIO. We use an I/O intensive program where nearly 100% of its overall runtime is spent writing to disk. We show that the use of FILCIO results in a speedup of 1.75x over the native approach, and extrapolate that the best improvement is when a program generates a large volume of small writes. FILCIO is available at https://github.com/jensenq/io_aggregation

Recognition of short linear motifs (SLiMs) or peptides by proteins is an important component of many cellular processes. However, due to limited and degenerate binding motifs, prediction of cellular targets is challenging. In addition, many of these interactions are transient and of relatively low affinity. Here, we focus on one of the largest families of SLiM‐binding domains in the human proteome, the PDZ domain. These domains bind the extreme C‐terminus of target proteins, and are involved in many signaling and trafficking pathways. To predict endogenous targets of PDZ domains, we developed MotifAnalyzer‐PDZ, a program that filters and compares all motif‐satisfying sequences in any publicly available proteome. This approach enables us to determine possible PDZ binding targets in humans and other organisms. Using this program, we predicted and biochemically tested novel human PDZ targets by looking for strong sequence conservation in evolution. We also identified three C‐terminal sequences in choanoflagellates that bind a choanoflagellate PDZ domain, the Monsiga brevicollis SHANK1 PDZ domain (mbSHANK1), with endogenously‐relevant affinities, despite a lack of conservation with the targets of a homologous human PDZ domain, SHANK1. All three are predicted to be signaling proteins, with strong sequence homology to cytosolic and receptor tyrosine kinases. Finally, we analyzed and compared the positional amino acid enrichments in PDZ motif‐satisfying sequences from over a dozen organisms. Overall, MotifAnalyzer‐PDZ is a versatile program to investigate potential PDZ interactions. This proof‐of‐concept work is poised to enable similar types of analyses for other SLiM‐binding domains (e.g., MotifAnalyzer‐Kinase). MotifAnalyzer‐PDZ is available at http://motifAnalyzerPDZ.cs.wwu.edu.

Interactive textbooks have great potential to increase student engagement with the course content which is critical to effective learning in computing education. Prior research on digital textbooks and interactive visualizations contributes to our understanding of student interactions with visualizations and modeling textbook knowledge concepts. However, research investigating student usage of interactive computing textbooks is still lacking. This study seeks to fill this gap by modeling student engagement with a Jupyter-notebook-based interactive textbook. Our findings suggest that students' active interactions with the presented interactive textbook, including changing, adding, and executing code in addition to manipulating visualizations, are significantly stronger in predicting student performance than conventional reading metrics. Our findings contribute to a deeper understanding of student interactions with interactive textbooks and provide guidance on the effective usage of said textbooks in computing education.

We explore how amino acid mutations affect the stability of the 306 residue main protease of the COVID-19 proteome. We employ two computational approaches, Site Directed Mutagenesis (SDM) and short runs of Molecular Dynamics. We focus our attention on residues 25-32 that make up a beta sheet of a canonical beta barrel close to an active site which includes Histidine 41. We considered this region a good candidate for mutations because such a large perturbation of a highly structured region close to the active site may prove to be highly detrimental to the protein's stability and may affect catalytic efficiency. Understanding how amino acid mutations affect the stability of the protein can inform efforts to develop pharmacological interventions. We mutated the 8 residues in silico to all other possible amino acids, and analyzed the resulting 152 mutants. Both computational methods predict that only a few specific mutations to some of the 8 residues have a major effect on the structural stability of the protein.

A mutation to the amino acid sequence of a protein can cause a biomolecule to be resistant to the intended effects of a drug. Assessing the changes of a drug's efficacy in response to mutations via mutagenesis wet-lab experiments is prohibitively time consuming for even a single point mutation, let alone for all possible mutations. Existing approaches for inferring mutation-induced drug resistance are available, but all of them reason about mutations of residues at or very near the protein-drug interface. However, there are examples of mutations far away from the region where the ligand binds, but which nonetheless render a protein resistant to the effects of the drug. We present a proof-of-concept computational pipeline that generates in silico the set of all possible single point mutations in a protein-ligand complex. We assess drug resistance via energy profiles for short runs of molecular dynamics of the mutants. We assess the impact of mutations far away from the protein-drug interface and provide case studies for exploring how amino acid substitutions both near and far away from where the ligand interacts with a protein target have a stabilizing or destabilizing effect on the protein-drug complex.

Bioinformatics software often integrates multiple off-the-shelf programs into a single compute pipeline. Each stand-alone program generates output, that is frequently saved into a plain-text file, which is then processed as input by the program that is responsible for the next stage of the computation. Modern advances in genome sequencing and protein structure resolution methods have yielded large amounts of data, that when processed by bioinformatics compute pipelines, results in vast numbers of file reads and writes. Since computation capabilities of large-scale distributed systems grow much faster than their I/O bandwidth, processing such big data using these compute pipelines will not scale as the amount of data grows. For this work, we motivate and demonstrate a dynamic interception-based I/O analysis tool to assess the file read and write characteristics of a protein mutation generation pipeline. We discuss how our analysis tool can be further extended to apply compression and in-site analysis and has the potential to scale I/O-intensive bioinformatics applications on high performance computing (HPC) systems.

A mutation to the amino acid sequence of a protein can cause a biomolecule to be resistant to the intended effects of a drug. Assessing the changes of a drug’s efficacy in response to mutations via mutagenesis wet-lab experiments is prohibitively time consuming for even a single point mutation, let alone for all possible mutations. Existing approaches for inferring mutation-induced drug resistance are available, but all of them reason about mutations of residues at or very near the protein-drug interface. However, there are examples of mutations far away from the region where the ligand binds, but which nonetheless render a protein resistant to the effects of the drug. We present a proof-of-concept computational pipeline that generates in silico the set of all possible single point mutations in a protein-ligand complex. We assess drug resistance using a graph theoretic rigidity analysis approach. Unlike existing methods, we are able to assess the impact of mutations far away from the protein-drug interface. We introduce several visualizations for exploring how amino acid substitutions both near and far away from where the ligand interacts with a protein target have a stabilizing or destabilizing effect on the protein-drug complex. We discuss our analytical approach in the context of experimental data from the literature about clinically known protein-drug interactions.

Understanding how an amino acid substitution affects a protein's structure can aid in the design of pharmaceutical drugs that aim at countering diseases caused by protein mutants. Unfortunately, performing even a few amino acid substitutions in vitro is both time and cost prohibitive, whereas an exhaustive analysis that involves systematically mutating all amino acids in the physical protein is infeasible. Computational methods have been developed to predict the effects of mutations, but even many of them are computationally intensive or are else dependent on homology or experimental data that may not be available for the protein being studied. In this work, we motivate and present a computation pipeline whose only input is a Protein Data Bank file containing the 3D coordinates of the atoms of a biomolecule. Our high-throughput approach uses our ProMuteHT algorithm to exhaustively generate in silico amino acid substitutions at each residue, and it also includes an energy minimization option. This is in contrast to our previous work, where we analyzed the effects of in silico mutations to Alanine, Serine, and Glycine only. We exploit the speed of a fast rigidity analysis approach to analyze our protein variants, and develop a Mutation Sensitivity (MuSe) Map, to permit identifying residues that are most sensitive to mutations. We present a case study to show the degree to which a MuSe Map and whisker plots are able to locate amino acids whose mutations most affect a protein's structure as inferred from a rigidity analysis approach.