Spatial arrangement and functional role of α subunits of proteasome activator PA28 in hetero-oligomeric form.
Biochem Biophys Res Commun
; 432(1): 141-5, 2013 Mar 01.
Article
en En
| MEDLINE
| ID: mdl-23376067
A major form of proteasome activator PA28 is a heteroheptamer composed of interferon-γ-inducible α and ß subunits, which share approximately 50% amino acid identity and possess distinct insert loops. This activator forms a complex with the 20S proteasome and thereby stimulates proteasomal degradation of peptides in an ATP-independent manner, giving rise to smaller antigenic peptides presented by major histocompatibility complex class I molecules. In this study, we performed biophysical and biochemical characterization of the structure and function of the PA28 hetero-oligomer. Deuteration-assisted small-angle neutron scattering demonstrated three α and four ß subunits are alternately arranged in the heptameric ring. In this arrangement, PA28 loops surround the central pore of the heptameric ring (site for peptide entry). Activating the 20S proteasome with a PA28 mutant that lacked the α subunit loops cleaved model substrates longer than a nonapeptide with better efficiency when compared to wild-type PA28. Based on these data, we hypothesize that the flexible PA28 loops act as gatekeepers, which function to select the length of peptide substrates to be transported between the proteolytic chamber and the extra-proteasomal medium.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Complejo de la Endopetidasa Proteasomal
Límite:
Animals
Idioma:
En
Revista:
Biochem Biophys Res Commun
Año:
2013
Tipo del documento:
Article
País de afiliación:
Japón
Pais de publicación:
Estados Unidos