Rigidifying a De Novo Enzyme Increases Activity and Induces a Negative Activation Heat Capacity.

Conformational sampling profoundly impacts the overall activity and temperature dependence of enzymes. Peroxidases have emerged as versatile platforms for high-value biocatalysis owing to their broad palette of potential biotransformations. Here, we explore the role of conformational sampling in mediating activity in the de novo peroxidase C45. We demonstrate that 2,2,2-triflouoroethanol (TFE) affects the equilibrium of enzyme conformational states, tending toward a more globally rigid structure. This is correlated with increases in both stability and activity. Notably, these effects are concomitant with the emergence of curvature in the temperature-activity profile, trading off activity gains at ambient temperature with losses at high temperatures. We apply macromolecular rate theory (MMRT) to understand enzyme temperature dependence data. These data point to an increase in protein rigidity associated with a difference in the distribution of protein dynamics between the ground and transition states. We compare the thermodynamics of the de novo enzyme activity to those of a natural peroxidase, horseradish peroxidase. We find that the native enzyme resembles the rigidified de novo enzyme in terms of the thermodynamics of enzyme catalysis and the putative distribution of protein dynamics between the ground and transition states. The addition of TFE apparently causes C45 to behave more like the natural enzyme. Our data suggest robust, generic strategies for improving biocatalytic activity by manipulating protein rigidity; for functional de novo protein catalysts in particular, this can provide more enzyme-like catalysts without further rational engineering, computational redesign, or directed evolution

Emergence of a Negative Activation Heat Capacity during Evolution of a Designed Enzyme

Temperature influences the reaction kinetics and evolvability of all enzymes. To understand how evolution shapes the thermodynamic drivers of catalysis, we optimized the modest activity of a computationally designed enzyme for an elementary proton-transfer reaction by nearly 4 orders of magnitude over 9 rounds of mutagenesis and screening. As theorized for primordial enzymes, the catalytic effects of the original design were almost entirely enthalpic in origin, as were the rate enhancements achieved by laboratory evolution. However, the large reductions in Δ were partially offset by a decrease in Δ and unexpectedly accompanied by a negative activation heat capacity, signaling strong adaptation to the operating temperature. These findings echo reports of temperature-dependent activation parameters for highly evolved natural enzymes and are relevant to explanations of enzymatic catalysis and adaptation to changing thermal environments

Selection of a Promiscuous Minimalist cAMP Phosphodiesterase from a Library of De Novo Designed Proteins

The ability of unevolved amino acid sequences to become biological catalysts was key to the emergence of life on earth. However, billions of years of evolution separate complex modern enzymes from their simpler early ancestors. To study how unevolved sequences can develop new functions, we screened for enzymatic activity in a collection of > 1 million novel sequences based on a de novo designed 4-helix bundle library of semi-random sequences. To mirror evolutionary selection for biological function, we screened the collection using ultrahigh-throughput droplet microfluidics to identify features that yield phosphoesterase activity. Characterization of active hits demonstrated that acquiring new function involved a large jump in sequence space: screening enriched for truncations that removed > 40% of the protein chain. This truncated protein dimerized into a dynamic -helical structure, consistent with the idea that gain of function was accompanied by an increase in structural dynamics relative to the parental 4-helix bundle. The purified protein catalyzes the hydrolysis of a range of phosphodiesters, with the greatest activity toward the biological second messenger cyclic AMP (cAMP). The novel cAMPase is a manganese-dependent metalloenzyme and catalyzes cAMP hydrolysis with a rate acceleration of 109 and catalytic proficiency on the order of >1014 M-1, comparable to larger enzymes shaped by billions of years of evolution. These findings suggest that fragmentation and effective shortening of protein length can be an unexpectedly fertile avenue for introducing structural and functional diversity into proteins

Comment on: "Computer Simulations Reveal an Entirely Entropic Activation Barrier for the Chemical Step in a Designer Enzyme"

Activation heat capacity has been proposed as an important factor in enzyme evolution and thermoadaptation. We previously demonstrated that the emergence of curved activity-temperature profiles during the evolution of a designer enzyme was due to the selective rigidification of its transition state ensemble that induced an activation heat capacity. angstrom qvist challenged our findings with molecular dynamics simulations suggesting that a change in the rate-limiting step underlies the experimental observations. As we describe here, angstrom qvist's model is not consistent with the experimental trends observed for the chemical step of the catalyzed reaction (kcat). We suggest that this discrepancy arises because the simulations performed by angstrom qvist were limited by restraints and short simulation times, which do not allow sampling of the motions responsible for the observed activation heat capacity.ISSN:2155-543

In vitro generated antibodies guide thermostable ADDomer nanoparticle design for nasal vaccination and passive immunization against SARS-CoV-2

International audienceAbstract Background Due to COVID-19, pandemic preparedness emerges as a key imperative, necessitating new approaches to accelerate development of reagents against infectious pathogens. Methods Here, we developed an integrated approach combining synthetic, computational and structural methods with in vitro antibody selection and in vivo immunization to design, produce and validate nature-inspired nanoparticle-based reagents against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Results Our approach resulted in two innovations: (i) a thermostable nasal vaccine called ADDoCoV, displaying multiple copies of a SARS-CoV-2 receptor binding motif derived epitope and (ii) a multivalent nanoparticle superbinder, called Gigabody, against SARS-CoV-2 including immune-evasive variants of concern (VOCs). In vitro generated neutralizing nanobodies and electron cryo-microscopy established authenticity and accessibility of epitopes displayed by ADDoCoV. Gigabody comprising multimerized nanobodies prevented SARS-CoV-2 virion attachment with picomolar EC50. Vaccinating mice resulted in antibodies cross-reacting with VOCs including Delta and Omicron. Conclusion Our study elucidates Adenovirus-derived dodecamer (ADDomer)-based nanoparticles for use in active and passive immunization and provides a blueprint for crafting reagents to combat respiratory viral infections