The proteasome is the main proteolytic system in the cytoplasm and nuclei of eukaryotic cells. It is responsible for degradation of short lived, damaged or mutated proteins, therefore it plays a critical function in the cell cycle control, apoptosis and many other biological processes. Impaired degradation mechanisms can lead to accumulation of damaged proteins, resulting in the development of aging processes [1]. Reduced activity of the proteasome underlies also the etiology of some neurodegenerative disorders such as Alzheimer's or Parkinson's disease. It is believed that low-molecular mass proteasome activators could prevent progression of age-related neurodegenerative disorders.
Blm10 is a yeast protein which is ATP- and ubiquitin-independent activator of the 20S proteasome. It stimulates hydrolysis of peptides and some partially unstructured proteins. The crystal structure of Blm10-yeast 20S complex revealed that C-terminal residues of Blm10 insert into the pocket between the α5 and α6 subunits of the 20S core particle, and their binding allows to partially open the gate that leads to the catalytic chamber of the proteasome [2].
Blm-pep is a 14-mer peptide designed based on the sequence of the C-terminal end of Blm10 protein. Blm-pep stimulates chymotrypsin-like activity of human 20S proteasome almost four times in tests with the low-molecular weight fluorogenic substrate Suc-LLVY-MCA, and several times in tests with the peptidic LFP substrate, which has been proved to not undergo proteolytic digestion by the latent proteasome. The crystal structure of the complex of Blm-pep and yeast 20S proteasome shows that Blm-pep docks into the same pocket as the C-terminus of Blm10 [3]. Based on molecular modelling studies and the crystal structures of Blm10-yeast 20S and Blm-pep-yeast 20S complexes, as well as the crystal structure of human 20S, we designed analogs of Blm-pep to obtain compounds with improved activity.
Acknowledgments:
This study was financially supported by NCN-funded grant 2014/15/B/NZ7/01014.