title: Operational definition of intrinsically unstructured protein sequences based on susceptibility to the 20S proteasome.
abstract: Intrinsically unstructured proteins (IUPs), also known as natively unfolded proteins, lack well-defined secondary and tertiary structure under physiological conditions. In recent years, growing experimental and theoretical evidence has accumulated, indicating that many entire proteins and protein sequences are unstructured under physiological conditions, and that they play significant roles in diverse cellular processes. Bioinformatic algorithms have been developed to identify such sequences in proteins for which structural data are lacking, but still generate substantial numbers of false positives and negatives. We describe here a simple and reliable in vitro assay for identifying IUP sequences based on their susceptibility to 20S proteasomal degradation. We show that 20S proteasomes digest IUP sequences, under conditions in which native, and even molten globule states, are resistant. Furthermore, we show that protein-protein interactions can protect IUPs against 20S proteasomal action. Taken together, our results thus suggest that the 20S proteasome degradation assay provides a powerful system for operational definition of IUPs.
authors: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors: Peter
authors: P
authors: Tsvetkov
authors: Gad
authors: G
authors: Asher
authors: Aviv
authors: A
authors: Paz
authors: Nina
authors: N
authors: Reuven
authors: Joel L
authors: JL
authors: Sussman
authors: Israel
authors: I
authors: Silman
authors: Yosef
authors: Y
authors: Shaul
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D019295:Computational Biology; D008722:Methods; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*
chemical_list: D011506:Proteins; D046988:Proteasome Endopeptidase Complex