HIERARCHICAL ASSEMBLY OF COILED-COIL PEPTIDES: PROTEIN INCLUSION AND SELF-REPLICATION
Peptides are versatile molecules with a wide range of functions in biological systems. Therefore, there is widespread interest in their use as a building block for the development of novel biomaterials. Many peptides have the capability to fold into supersecondary structures such as collagen triple helices and coiled-coils. These peptides are of particular interest to many researchers due to their tunable stability and capability to display different motifs to promote assembly on designated faces of the building block. Herein we describe two distinct studies utilizing the self-assembly of a trimeric coiled-coil. One study involves the designed metal-mediated coiled-coil assembly into crystals capable of stabilizing protein guests, while the other involves a coiled-coil system capable of self-assembly and self-replication.
First, we detail three-dimensional (3D) coiled coil peptide crystals with metal ions that include and overgrow His-tagged fluorescent proteins within the crystal. The protein guests are found within two symmetry-related growth sectors of the crystalline host that are associated with faces of the growing crystal that display ligands for metal ions. The fluorescent proteins are included within this “hourglass” region of the crystals at a notably high level, display order within the crystal hosts, and demonstrate sufficiently tight packing to enable energy transfer between a donor-acceptor pair. His-tagged fluorescent proteins display remarkable thermal stability to denaturation over extended periods of time (days) at high temperatures when within the crystals. Ultimately this strategy may prove useful for the prolonged storage of thermally sensitive biopolymer guests within a 3D crystalline matrix.
Second, we describe our work towards developing a coiled-coil peptide capable of both self-replication and self-assembly, two major requirements for the existence of pre-biotic systems. Coiled-coil peptides have previously displayed the capability of either self-replication or self-assembly separately. Herein, we designed cysteine containing mutants of a self-assembling trimer based on the GCN4 leucine zipper. After exploring the self-assembling properties of these mutant peptides, we examine how two peptide fragments can ligate and subsequently self-assemble into larger fibrillar structures.