PA28αβ reduces size and increases hydrophilicity of 20S immunoproteasome peptide products

Item Type:	Article
Title:	PA28αβ reduces size and increases hydrophilicity of 20S immunoproteasome peptide products
Creators Name:	Raule, M. and Cerruti, F. and Benaroudj, N. and Migotti, R. and Kikuchi, J. and Bachi, A. and Navon, A. and Dittmar, G. and Cascio, P.
Abstract:	The specific roles that immunoproteasome variants play in MHC class I antigen presentation are unknown at present. To investigate the biochemical properties of different immunoproteasome forms and unveil the molecular mechanisms of PA28 activity, we performed in vitro degradation of full-length proteins by 20S, 26S, and PA28{alpha}{beta}-20S immunoproteasomes and analyzed the spectrum of peptides released. Notably, PA28{alpha}{beta}-20S immunoproteasomes hydrolyze proteins at the same low rates as 20S alone, which is in line with PA28, neither stimulating nor preventing entry of unfolded polypeptides into the core particle. Most importantly, binding of PA28{alpha}{beta} to 20S greatly reduces the size of proteasomal products and favors the release of specific, more hydrophilic, longer peptides. Hence, PA28{alpha}{beta} may either allosterically modify proteasome active sites or act as a selective "smart" sieve that controls the efflux of products from the 20S proteolytic chamber.
Keywords:	Allosteric Regulation, Catalytic Domain, Hydrophobic and Hydrophilic Interactions, Particle Size, Proteasome Endopeptidase Complex, Tandem Mass Spectrometry
Source:	Chemistry & Biology
ISSN:	1074-5521
Publisher:	Cell Press / Elsevier
Volume:	21
Number:	4
Page Range:	470-480
Date:	24 April 2014
Official Publication:	https://doi.org/10.1016/j.chembiol.2014.02.006
PubMed:	View item in PubMed

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