2 Institute of Biotechnology, Czech Academy of Sciences, Průmyslová 595, 252 50 Vestec, Czechia
Evolution has optimized protein variants with respect to the life of an organism in its surroundings. For example, protein variants in bacteria living in high temperatures have usually higher thermal stability than those of bacteria living in arctic environments. Higher thermal stability is frequently required in biotechnologies as this usually goes hand in hand with increased stability in various denaturing agents, natural environment, and with higher expression yields.
Human interleukin 24 has a potential in treatment for autoimmune diseases and cancer [1]. It is a relatively instable protein, and its expression usually provides low yields. We designed optimized variants using the PROSS algorithm [2], performed various biophysical and function studies, and successfully crystallized more stable variant having 30 point mutations (~ 20 % of all amino acids). We determined the crystal structure at 1.3-Å resolution. The crystal structure explains
Unfortunately, this protein variant lost some of its functions that are related to binding its biological interaction partners IL-20R1 and IL-22R1. However, the function was restored to 80 % of its wild-type variant with a single reverse mutation to the wild-type residue Thr198. Such protein variant can be used for further optimization and subsequent application in clinical studies.