Download MendeleyOptimal TELSAM-Target Protein Linker Character is Target Protein-Dependent.
Romo, M.J.P., Keliiliki, A., Averett, J.C., Gonzalez, J.F., Noakes, E., Wilson, E.W., Smith, C., Averett, B., Hansen, D., Nickles, R., Bradford, M., Soleimani, S., Smith, T., Nawarathnage, S., Samarwickrama, P., Kelsch, A., Bunn, D., Stewart, C., Abiodun, W., Tsubaki, E., Brown, S., Doukov, T.I., Moody, J.D.(2025) bioRxiv
- PubMed: 40950120
- DOI: https://doi.org/10.1101/2025.08.29.672704
- Primary Citation of Related Structures:
9DB5, 9DVG - PubMed Abstract:
Fusing a variant of the sterile alpha motif domain of the human translocation ETS leukaemia protein (TELSAM) to a protein of interest has been shown to significantly enhance crystallization propensity. TELSAM is a pH-dependent, polymer-forming protein crystallization chaperone which, when covalently fused to a protein of interest, forms a stable, well-ordered crystal lattice. However, despite its success, a challenge persists in that crystal quality and diffraction limits appear to be heavily dependent on the choice of linker between TELSAM and the protein of interest, with identification of a functional linker relying on trial-and-error methods. Likewise, previous studies revealed that the 10xHis tag at the TELSAM N-terminus can either facilitate or hinder the ordered crystallization of target proteins attached via flexible or semi-flexible linkers. To address these challenges, we designed multiple constructs with several types of linkers-rigid (helical fusion), semi-flexible (Pro-Ala n ), and flexible (poly-Gly)-of varying lengths to fuse a designed ankyrin repeat protein (DARPin) to the TELSAM C-terminus. Semi-flexible and flexible linker constructs were made with and without the 10xHis tag. Our findings indicate that short semi-flexible and rigid linkers consistently yield large crystals within 24 hours with a DARPin target protein, but that flexible linkers perform best with a TNK1 UBA domain target protein. Removing the 10xHis tag enhanced crystallization rates, improved crystal morphology, and increased the crystallization propensity of semi-flexible and flexible linker constructs. While removing the His tag did not have a significant effect on crystal size, it improved the diffraction limits and crystal quality of the 1TEL-PA-DARPin construct. These results suggest that the ideal linker selection primarily depends on the properties of the target protein. Our data support the recommendation to use a short yet flexible or semi-flexible linker between TELSAM and the target protein to facilitate protein crystallization and high-resolution structure determination. In this study, we examine the effect of short to medium-length flexible, semi-flexible, and rigid linkers on the crystallization of a DARPin fused to the 1TEL protein crystallization chaperone, demonstrating that while rigid linkers impair crystallization and reduce diffraction quality, the ideal linker character remain target-protein dependent.
