Structure and Function of Proteins from Extremophiles.

Complementary to our research on extremophiles is our continuing investigation of protein structure-function relationships under the expanded pressure and temperature space afforded by stability of these extremophilic proteins. We have previously found that many thermophilic enzymes are substantially stabilized at high temperatures by high pressure. This effect appears to correlate with the internal hydrophobicity and/or the structural rigidity of the protein. High-pressure studies have thus helped to elucidate the importance of hydrophobic interactions and internal flexibility in protein stabilization. Significant activation by pressure has also been observed for some thermophilic proteins.

In recent years, our lab has focused on describing the protein folding and degradative machinery in extremophiles with the aim of exploiting such stable proteins for industrially important applications. Our recent work on proteins from extremophiles has produced important results that bridge the fields of protein engineering and biomaterials. A central aim of this research is to harness the potential of proteins as building blocks for the construction of tailor-made scaffolds and templates. For example, we recently characterized the high thermal stability of a filamentous protein template, the g-prefoldin (ɣ-PFD) from the hyperthermophile Methanocaldococcus jannaschii, and subsequently used rational design to further enhance the filament’s thermal stability for application as a biotemplate in the creation of platinum nanowires. These enhanced filaments functioned as templates for the synthesis of platinum nanowires at unprecedented temperatures, and may create new opportunities for other applications of nanoscale biotempates that require exceptional thermal stability.

Currently we are redesigning the modular subunits of the ɣ-PFD (including its TERM variant) with the overall goal of generating proteins that assemble into 2D and 3D shapes of predictable and controllable dimensions. To that end, we have discovered a novel heat shock-inducible chaperone, ɣ-prefoldin, which forms extended filaments. In related studies, we have found that the stability of chaperones in miscible organic co-solvents correlates with melting temperature in aqueous solution, and have practically utilized this effect for applications ranging from antibiotic synthesis to biofuels production.

The emerging interface of biology and materials science is creating new opportunities for the design, synthesis, and optimization of biologically-enabled and biologically-inspired materials. For example, the incorporation of proteins into polymers can result in hybrid materials that combine the properties of the polymer as a cost-effective and easy to process material with the highly evolved biological functionality of the protein, enabling new concepts for construction of sensors and biomedical materials. We have recently proven the concept of a protein-based nanosensor that is able to report deformation of the embedding polymer matrix. We combined the structural properties of a chaperonin from a thermophilic organism with the spectral properties of fluorescent proteins in order to generate a protein complex that exhibits fluorescent energy resonance transfer (FRET) and is sensitive to structural deformation. Such self-reporting materials could be used in myriad applications where easy and early detection of damage is essential to avoid catastrophic failure of the material.

Extended filaments formed by the extremophilic chaperone, g-prefoldin

Mechanical nanosensor based on FRET within a thermosome for damage-reporting polymeric materials