The ability to design synthetic protein-protein interactions provides an important tool in creating synthetic networks for the regulation of the cellular response and numerous other functions, such as localization and construction of cellular structures. Additional tools for the regulation of protein assemblies would have strong impact on science, both as a tool for research as well as for versatile applications, from biotech to therapy.
Four helical bundles are protein domains that can be designed and have been used to mediate protein (hetero)dimerization based on splitting them into two subdomains each comprising two helices.
For this PhD work we decided to further investigate the potentials of diverse segmentation strategy of a de novo designed four helical bundle (4HB) as a platform for generation dimerization, trimerization and tetramerization modules from a single protein. Segmentation strategy can thus extend the repertoire of orthogonal oligomerization domains from a single 4HB structures and reduces the need for de novo designs. We provide a demonstration of generalizability of segmentation strategy on several four helical bundles. Additionally, segmentation provides further detail in four helical bundle structure assembly and contribution of each of the four single peptides to its formation. This information has been often overlooked in the protein design workflow, where only the stability of final structure is assessed.
In addition to its value for the investigation of designed structures, newly generated oligomerization modules have potentials for diverse biological applications. We have evaluated the level of affinity of designed oligomerization modules and reconstitution into designed four helical bundle based on split firefly luciferase reconstitution and activation. Further, we demonstrated in mammalian cells, that they can act as mediators of information towards diverse biological processes, such as: simultaneous and independent regulation of gene expression via the TALE-VP16 system; rapalog dependent inducible activation of split firefly luciferase reconstitution and construction of a SbMVp-PPVp protease cascade; and detection of CD19 and CD20 ligands on the surface of cancer cells with signal transduction into CAR-T cells in the field of immunotherapy.
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