Structure--function relationships in bovine thymus 20S proteasome: a fluorimetric study.
The structure--function relationships occurring on the bovine thymus 20S proteasome, which exhibits the features of an immunoproteasome, have been studied. The investigation has been performed, essentially, using a fluorimetric approach, taking advantage either of the sensitivity of the complex to sodium dodecil sulfate and chaotropic agents (urea and guanidine hydrochloride) or of the presence, on the molecule, of a high number of tryptophan residues. The results obtained indicate that the perturbation or the oxidation of these residues affect the catalytic events taking place on the thymus proteasome and that the functional effects determined by SDS and chaotropic agents most likely occur through a series of progressive structural modifications leading to an inactive molecule. The presence of structural intermediates in the proteasome inactivation process suggests that thymus proteasome is a molecule characterized, at the same time, by structural flexibility (modulation of active sites) and structural stability (maintaining of the quaternary structure) in agreement with its crucial role in the cell life cycle.
Eleuteri
A M
AM
Department of Molecular, Cellular and Animal Biology, Post-graduate School of Clinical Biochemistry, University of Camerino, 62032 Camerino MC, Italy. a.eleuteri@cambio.unicam.it
Lupidi
G
G
Angeletti
M
M
Amici
M
M
Marchini
C
C
Pucciarelli
S
S
Fioretti
E
E
D000818:Animals; D002417:Cattle; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D005453:Fluorescence; D005470:Fluorometry / Q000379:methods; D019791:Guanidine; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011489:Protein Denaturation; D012967:Sodium Dodecyl Sulfate; D013329:Structure-Activity Relationship; D013950:Thymus Gland / Q000201:enzymology; D014508:Urea
D009097:Multienzyme Complexes; D012967:Sodium Dodecyl Sulfate; D014508:Urea; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D019791:Guanidine