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Publication Abstract from PubMed

Recent bioinformatic analyses identified proteasome assembly chaperone-like proteins, PbaA and PbaB, in archaea. PbaB forms a homotetramer and functions as a proteasome activator, whereas PbaA does not interact with the proteasome despite the presence of an apparent C-terminal proteasome activation motif. We revealed that PbaA forms a homopentamer predominantly in the closed conformation with its C-terminal segments packed against the core domains, in contrast to the PbaB homotetramer with projecting C-terminal segments. This prompted us to create a novel proteasome activator based on a well-characterized structural framework. We constructed a panel of chimeric proteins comprising the homopentameric scaffold of PbaA and C-terminal segment of PbaB and subjected them to proteasome-activating assays as well as small-angle X-ray scattering and high-speed atomic force microscopy. The results indicated that the open conformation and consequent proteasome activation activity could be enhanced by replacement of the crystallographically disordered C-terminal segment of PbaA with the corresponding disordered segment of PbaB. Moreover, these effects can be produced just by incorporating two glutamate residues into the disordered C-terminal segment of PbaA, probably due to electrostatic repulsion among the negatively charged segments. Thus, we successfully endowed a functionally undefined protein with proteasome-activating activity by modifying its C-terminal segment.

Conversion of functionally undefined homopentameric protein PbaA into a proteasome activator by mutational modification of its C-terminal segment conformation.,Yagi-Utsumi M, Sikdar A, Kozai T, Inoue R, Sugiyama M, Uchihashi T, Yagi H, Satoh T, Kato K Protein Eng Des Sel. 2017 Dec 28. pii: 4781309. doi: 10.1093/protein/gzx066. PMID:29301037^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.