We studied the usefulness of genetic fusion to TELSAM polymers as an effective protein crystallization strategy. We observed novel properties in crystals of two TELSAM-target protein fusions. TELSAM as a crystallization chaperone shows rapid crystallization when it's fused to target proteins and possibly with a greater propensity. Some TELSAM-target fusions crystallized more rapidly than the same target protein alone. TELSAM-target proteins can be crystallized at relatively low protein concentrations such as 0.1 mg/mL. TELSAM requires no TELSAM polymers touching one another in the crystal lattice in order to form well-diffracting crystals. This lack of crystal contacts has not been observed in previously reported TELSAM crystal structures. Flexible TELSAM-target protein linkers can allow target proteins to find productive binding modes against the TELSAM polymer. This study tested TELSAM linker lengths varying by the number of glycines, such as 2xGly, 4xGly, 6xGly, 8xGly, and 10xGly. Only TELSAM fused to UBA with 2 and 4 glycine linkers were crystalized. TELSAM polymers can adjust their helical rise to allow fused target proteins to make productive crystal contacts, and fusion to TELSAM polymers increases avidity to stabilize weak inter-target protein crystal contacts. In conclusion, we report features of TELSAM-target protein crystal structures and outline future work needed to validate TELSAM as a crystallization chaperone and define the best practices for its use.

Structural biology uncovers life's secrets by studying protein structures via techniques like X-ray crystallography. This knowledge drives advancements in protein engineering for the improvement of human lives. Yet, obtaining high-quality crystals in X-ray crystallography is challenging. To overcome this, we used Translocation ETS Leukemia protein Sterile Alpha Motif domain (TELSAM), a promising polymer-forming crystallization chaperone (PFCC), to enhance protein crystallization. Human thirty-eight-negative kinase-1 (TNK1), a key player in cancer progression, possess a ubiquitin association (UBA) domain that binds polyubiquitin and regulates TNK1 activity and stability. Although sequence analysis hints at an unconventional TNK1 UBA domain architecture, its molecular structure lacks experimental validation. To gain insight into TNK1 regulation, we fused the UBA domain to the 1TEL crystallization chaperone and obtained crystals diffracting as far as 1.53 Ã…. 1TEL enabled solution of the X-ray phases. GG and GSGG linkers allowed the UBA to reproducibly find a productive binding mode against its 1TEL polymer and to crystallize at protein concentrations as low as 0.1 mg/mL. Our findings support a TELSAM fusion crystallization mechanism, highlighting fewer crystal contacts compared to traditional crystals. Both modeling and experimental validation indicate that the UBA domain exhibits selectivity towards polyubiquitin chain length and linkages. Radical S-adenosylmethionine (SAM) enzymes catalyze various radical-mediated substrate transformations. Despite the growing interest of computational enzyme design in industrial small molecule synthesis, radical SAM enzymes remain relatively unexplored. We used PyRosetta to leverage hydrogen bonding design (hbDes) and hydrophobic interaction design (hpDes) to enable a radical cyclization reaction on our selected substrate. Although the purified enzymes demonstrated activation potential with a reducing agent, enzymatic assays failed to exhibit activity against the reactant. To obtain successful results, addressing additional questions and issues is required, which may involve the implementation of machine learning.