A spindle and thread-mechanism unblocks translation of N-terminally disordered proteins

Protein disorder is a major hurdle for structural biology. A prominent example is the tumour suppressor p53, whose low expression levels and poor conformational stability due to a high degree of disorder pose major challenges to the development of cancer therapeutics. Here, we address these issues by fusing p53 to an engineered spider silk domain termed NT*. The chimeric protein displays highly efficient translation in vitro and in E. coli and is fully active in human cancer cells. The transmission electron microscopy structure and native mass spectrometry reveal that the full-length p53 fusion protein adopts a compact conformation. Molecular dynamics simulations show that the disordered transactivation domain of p53 is wound around the NT* domain via a series of folding events, resulting in a globular structure. We find that expression of B-Raf, another partially disordered cancer target, is similarly enhanced by fusion to NT*. In summary, we demonstrate how inducing co-translational folding via a molecular "spindle and thread" mechanism can overcome poor translation efficiency of partially disordered proteins.