Biophysical Society Thematic Meeting - October 25-30, 2015

Polymers and Self Assembly: From Biology to Nanomaterials

Thursday Speaker Abstracts

Bacterial Strategies for Protein Self-Assembly at Interfaces Cait MacPhee University of Cambridge, United Kingdom No abstract

Self-Assembly of Protein Nanofibrils that Display Active Enzymes Sarah Perrett . Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.

The ability of proteins to self-assemble into beta-sheet-rich aggregates called amyloid fibrils is considered to be universal, although certain polypeptide sequences have a particularly high propensity to adopt these conformations. In many cases the formation of amyloid fibrils is deleterious and associated with the progression of disease, but there are also examples of proteins for which the cross-beta structure represents the functional conformation. Ure2 is the protein determinant of the yeast prion [URE3]. Ure2 consists of an N-terminal prion-inducing domain that is disordered in the native state, whereas the C-terminal functional domain has a globular fold with structural similarity to glutathione transferase enzymes. The C-terminal domain shows enzymatic activity in both the soluble and fibrillar forms of Ure2. We have used a variety of biophysical approaches to investigate the structure of Ure2 fibrils and their mechanism of assembly. We have also created chimeric constructs where the prion domain is genetically fused to other enzymes of different sizes and architectures. These chimeric polypeptide constructs spontaneously self-assemble into nanofibrils with fused active enzyme subunits displayed on the amyloid fibril surface. We can measure steady-state kinetic parameters for the appended enzymes in situ within fibrils, and compare these for the identical protein constructs in solution. We have also applied microfluidic techniques to form enzymatically-active microgel particles from the chimeric self-assembling protein nanofibrils. The use of scaffolds formed from biomaterials that self-assemble under mild conditions enables the formation of catalytic microgels whilst maintaining the integrity of the encapsulated enzyme. In combination with microfluidic trapping techniques, these approaches illustrate the potential of self-assembling materials for enzyme immobilization and recycling, and for biological flow-chemistry. The design principles can be adopted to create countless other bioactive amyloid-based materials with diverse functions.

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