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ELife Apr 2020Two interpretations of similar structures for the same molecular machine illustrate the limits of inferring biochemical mechanism from protein structure.
Two interpretations of similar structures for the same molecular machine illustrate the limits of inferring biochemical mechanism from protein structure.
Topics: Models, Molecular; Proteolysis
PubMed: 32321627
DOI: 10.7554/eLife.56501 -
BioEssays : News and Reviews in... Jun 2022Molecular chaperones in cells constantly monitor and bind to exposed hydrophobicity in newly synthesized proteins and assist them in folding or targeting to cellular... (Review)
Review
Molecular chaperones in cells constantly monitor and bind to exposed hydrophobicity in newly synthesized proteins and assist them in folding or targeting to cellular membranes for insertion. However, proteins can be misfolded or mistargeted, which often causes hydrophobic amino acids to be exposed to the aqueous cytosol. Again, chaperones recognize exposed hydrophobicity in these proteins to prevent nonspecific interactions and aggregation, which are harmful to cells. The chaperone-bound misfolded proteins are then decorated with ubiquitin chains denoting them for proteasomal degradation. It remains enigmatic how molecular chaperones can mediate both maturation of nascent proteins and ubiquitination of misfolded proteins solely based on their exposed hydrophobic signals. In this review, we propose a dynamic ubiquitination and deubiquitination model in which ubiquitination of newly synthesized proteins serves as a "fix me" signal for either refolding of soluble proteins or retargeting of membrane proteins with the help of chaperones and deubiquitinases. Such a model would provide additional time for aberrant nascent proteins to fold or route for membrane insertion, thus avoiding excessive protein degradation and saving cellular energy spent on protein synthesis. Also see the video abstract here: https://youtu.be/gkElfmqaKG4.
Topics: Molecular Chaperones; Protein Folding; Protein Transport; Ubiquitin; Ubiquitination
PubMed: 35357021
DOI: 10.1002/bies.202200014 -
Methods in Molecular Biology (Clifton,... 2022Thermofluor is a fluorescence-based thermal shift assay, which measures temperature-induced protein unfolding and thereby yields valuable information about the integrity...
Thermofluor is a fluorescence-based thermal shift assay, which measures temperature-induced protein unfolding and thereby yields valuable information about the integrity of a purified recombinant protein. Analysis of ligand binding to a protein is another popular application of this assay. Thermofluor requires neither protein labeling nor highly specialized equipment, and can be performed in a regular real-time PCR instrument. Thus, for a typical molecular biology laboratory, Thermofluor is a convenient method for the routine assessment of protein quality. Here, we provide Thermofluor protocols using the example of Cdc123. This ATP-grasp protein is an essential assembly chaperone of the eukaryotic translation initiation factor eIF2. We also report on a destabilized mutant protein version and on the ATP-mediated thermal stabilization of wild-type Cdc123 illustrating protein integrity assessment and ligand binding analysis as two major applications of the Thermofluor assay.
Topics: Adenosine Triphosphate; Eukaryotic Initiation Factor-2; Ligands; Protein Binding; Protein Unfolding; Recombinant Proteins
PubMed: 35796993
DOI: 10.1007/978-1-0716-2501-9_15 -
Protein unfolding by SDS: the microscopic mechanisms and the properties of the SDS-protein assembly.Nanoscale Mar 2020The effects of detergent sodium dodecyl sulfate (SDS) on protein structure and dynamics are fundamental to the most common laboratory technique used to separate proteins...
The effects of detergent sodium dodecyl sulfate (SDS) on protein structure and dynamics are fundamental to the most common laboratory technique used to separate proteins and determine their molecular weights: polyacrylamide gel electrophoresis. However, the mechanism by which SDS induces protein unfolding and the microstructure of protein-SDS complexes remain largely unknown. Here, we report a detailed account of SDS-induced unfolding of two proteins-I27 domain of titin and β-amylase-obtained through all-atom molecular dynamics simulations. Both proteins were found to spontaneously unfold in the presence of SDS at boiling water temperature on the time scale of several microseconds. The protein unfolding was found to occur via two distinct mechanisms in which specific interactions of individual SDS molecules disrupt the protein's secondary structure. In the final state of the unfolding process, the proteins are found to wrap around SDS micelles in a fluid necklace-and-beads configuration, where the number and location of bound micelles changes dynamically. The global conformation of the protein was found to correlate with the number of SDS micelles bound to it, whereas the number of SDS molecules directly bound to the protein was found to define the relaxation time scale of the unfolded protein. Our microscopic characterization of SDS-protein interactions sets the stage for future refinement of SDS-enabled protein characterization methods, including protein fingerprinting and sequencing using a solid-state nanopore.
Topics: Connectin; Micelles; Molecular Dynamics Simulation; Protein Structure, Secondary; Protein Unfolding; Sodium Dodecyl Sulfate; Temperature; alpha-Amylases
PubMed: 32080694
DOI: 10.1039/c9nr09135a -
Biomolecules Feb 2020As a tribute to Professor Oleg B. Ptitsyn, we organized an interview with Professor Akiyoshi Wada held in Tokyo in the middle of September 2019. Both Professor A. Wada...
As a tribute to Professor Oleg B. Ptitsyn, we organized an interview with Professor Akiyoshi Wada held in Tokyo in the middle of September 2019. Both Professor A. Wada and the late Professor O. B. Ptitsyn greatly contributed to the field of protein biophysics, and they played leading roles in establishing the concept of the "Molten Globule state" 35-40 years ago. This editorial is intended to recount, as accurately as possible, some episodes during the early days of protein research that led to the discovery of this state, and how this concept was coined the "Molten Globule state" and came to be widely accepted by biophysicists, biochemists, and molecular biologists.
Topics: Amino Acid Sequence; Biophysical Phenomena; Circular Dichroism; History, 20th Century; Models, Molecular; Protein Biosynthesis; Protein Conformation; Protein Denaturation; Protein Folding; Proteins; Thermodynamics
PubMed: 32050721
DOI: 10.3390/biom10020269 -
Chemical Science Nov 2019Interactions between proteins and surfactants are of relevance in many applications including food, washing powder formulations, and drug formulation. The anionic...
Interactions between proteins and surfactants are of relevance in many applications including food, washing powder formulations, and drug formulation. The anionic surfactant sodium dodecyl sulfate (SDS) is known to unfold globular proteins, while the non-ionic surfactant octaethyleneglycol monododecyl ether (CE) can be used to refold proteins from their SDS-denatured state. While unfolding have been studied in detail at the protein level, a complete picture of the interplay between protein and surfactant in these processes is lacking. This gap in our knowledge is addressed in the current work, using the β-sheet-rich globular protein β-lactoglobulin (bLG). We combined stopped-flow time-resolved SAXS, fluorescence, and circular dichroism, respectively, to provide an unprecedented in-depth picture of the different steps involved in both protein unfolding and refolding in the presence of SDS and CE. During unfolding, core-shell bLG-SDS complexes were formed within ∼10 ms. This involved an initial rapid process where protein and SDS formed aggregates, followed by two slower processes, where the complexes first disaggregated into single protein structures situated asymmetrically on the SDS micelles, followed by isotropic redistribution of the protein. Refolding kinetics (>100 s) were slower than unfolding (<30 s), and involved rearrangements within the mixing deadtime (∼5 ms) and transient accumulation of unfolded monomeric protein, differing in structure from the original bLG-SDS structure. Refolding of bLG involved two steps: extraction of most of the SDS from the complexes followed by protein refolding. These results reveal that surfactant-mediated unfolding and refolding of proteins are complex processes with rearrangements occurring on time scales from sub-milliseconds to minutes.
PubMed: 34123043
DOI: 10.1039/c9sc04831f -
Nature Communications Jan 2022Engineering shape memory/morphing materials have achieved considerable progress in polymer-based systems with broad potential applications. However, engineering...
Engineering shape memory/morphing materials have achieved considerable progress in polymer-based systems with broad potential applications. However, engineering protein-based shape memory/morphing materials remains challenging and under-explored. Here we report the design of a bilayer protein-based shape memory/morphing hydrogel based on protein folding-unfolding mechanism. We fabricate the protein-bilayer structure using two tandem modular elastomeric proteins (GB1) and (FL). Both protein layers display distinct denaturant-dependent swelling profiles and Young's moduli. Due to such protein unfolding-folding induced changes in swelling, the bilayer hydrogels display highly tunable and reversible bidirectional bending deformation depending upon the denaturant concentration and layer geometry. Based on these programmable and reversible bending behaviors, we further utilize the protein-bilayer structure as hinge to realize one-dimensional to two-dimensional and two-dimensional to three-dimensional folding transformations of patterned hydrogels. The present work will offer new inspirations for the design and fabrication of novel shape morphing materials.
Topics: Amino Acid Sequence; Elastic Modulus; Elastomers; Hydrogels; Polymers; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Protein Engineering; Protein Folding; Protein Unfolding; Proteins; Wettability
PubMed: 35013234
DOI: 10.1038/s41467-021-27744-0 -
Nature May 2023CrAssphage and related viruses of the order Crassvirales (hereafter referred to as crassviruses) were originally discovered by cross-assembly of metagenomic sequences....
CrAssphage and related viruses of the order Crassvirales (hereafter referred to as crassviruses) were originally discovered by cross-assembly of metagenomic sequences. They are the most abundant viruses in the human gut, are found in the majority of individual gut viromes, and account for up to 95% of the viral sequences in some individuals. Crassviruses are likely to have major roles in shaping the composition and functionality of the human microbiome, but the structures and roles of most of the virally encoded proteins are unknown, with only generic predictions resulting from bioinformatic analyses. Here we present a cryo-electron microscopy reconstruction of Bacteroides intestinalis virus ΦcrAss001, providing the structural basis for the functional assignment of most of its virion proteins. The muzzle protein forms an assembly about 1 MDa in size at the end of the tail and exhibits a previously unknown fold that we designate the 'crass fold', that is likely to serve as a gatekeeper that controls the ejection of cargos. In addition to packing the approximately 103 kb of virus DNA, the ΦcrAss001 virion has extensive storage space for virally encoded cargo proteins in the capsid and, unusually, within the tail. One of the cargo proteins is present in both the capsid and the tail, suggesting a general mechanism for protein ejection, which involves partial unfolding of proteins during their extrusion through the tail. These findings provide a structural basis for understanding the mechanisms of assembly and infection of these highly abundant crassviruses.
Topics: Humans; Capsid; Cryoelectron Microscopy; DNA Viruses; Virion; Virus Assembly; Intestines; Viral Proteins; Protein Unfolding; Protein Folding
PubMed: 37138077
DOI: 10.1038/s41586-023-06019-2 -
Analytical Chemistry Mar 2020In modern biochemistry, protein stability and ligand interactions are of high interest. These properties are often studied with methods requiring labeled biomolecules,...
In modern biochemistry, protein stability and ligand interactions are of high interest. These properties are often studied with methods requiring labeled biomolecules, as the existing methods utilizing luminescent external probes suffer from low sensitivity. Currently available label-free technologies, e.g., thermal shift assays, circular dichroism, and differential scanning calorimetry, enable studies on protein unfolding and protein-ligand interactions (PLI). Unfortunately, the required micromolar protein concentration increases the costs and predisposes these methods for spontaneous protein aggregation. Here, we report a time-resolved luminescence method for protein unfolding and PLI detection with nanomolar sensitivity. The Protein-Probe method is based on highly luminescent europium chelate-conjugated probe, which is the key component in sensing the hydrophobic regions exposed to solution after protein unfolding. With the same Eu-probe, we also demonstrate ligand-interaction induced thermal stabilization with model proteins. The developed Protein-Probe method provides a sensitive approach overcoming the problems of the current label-free methodologies.
Topics: Ligands; Models, Molecular; Protein Binding; Protein Denaturation; Protein Stability; Protein Structure, Secondary; Proteins; Temperature; Transition Temperature
PubMed: 32013400
DOI: 10.1021/acs.analchem.9b05712 -
Biophysical Journal Jun 2021Every amino acid residue can influence a protein's overall stability, making stability highly susceptible to change throughout evolution. We consider the distribution of...
Every amino acid residue can influence a protein's overall stability, making stability highly susceptible to change throughout evolution. We consider the distribution of protein stabilities evolutionarily permittable under two previously reported protein fitness functions: flux dynamics and misfolding avoidance. We develop an evolutionary dynamics theory and find that it agrees better with an extensive protein stability data set for dihydrofolate reductase orthologs under the misfolding avoidance fitness function rather than the flux dynamics fitness function. Further investigation with ribonuclease H data demonstrates that not any misfolded state is avoided; rather, it is only the unfolded state. At the end, we discuss how our work pertains to the universal protein abundance-evolutionary rate correlation seen across organisms' proteomes. We derive a closed-form expression relating protein abundance to evolutionary rate that captures Escherichia coli, Saccharomyces cerevisiae, and Homo sapiens experimental trends without fitted parameters.
Topics: Evolution, Molecular; Humans; Protein Folding; Protein Stability; Protein Unfolding; Proteome; Saccharomyces cerevisiae
PubMed: 33932438
DOI: 10.1016/j.bpj.2021.03.042