Molecular basis for phosphorylation-dependent, PEST-mediated protein turnover.
Proteasomal-mediated rapid turnover of proteins is often modulated by phosphorylation of PEST sequences. The E2 protein from papillomavirus participates in gene transcription, DNA replication, and episomal genome maintenance. Phosphorylation of a PEST sequence located in a flexible region accelerates its degradation. NMR analysis of a 29 amino acid peptide fragment derived from this region shows pH-dependent polyproline II and alpha helix structures, connected by a turn. Phosphorylation, in particular that at serine 301, disrupts the overall structure, and point mutations have either stabilizing or destabilizing effects. There is an excellent correlation between the thermodynamic stability of different peptides and the half-life of E2 proteins containing the same mutations in vivo. The structure around the PEST region appears to have evolved a marginal stability that is finely tunable by phosphorylation. Thus, conformational stability, rather than recognition of a phosphate modification, modulates the degradation of this PEST sequence by the proteasome machinery.
Instituto Leloir, Patricias Argentinas 435, (1405) Buenos Aires, Argentina.
Maria M
MM
García-Alai
Mariana
M
Gallo
Marcelo
M
Salame
Diana E
DE
Wetzler
Alison A
AA
McBride
Maurizio
M
Paci
Daniel O
DO
Cicero
Gonzalo
G
de Prat-Gay
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011099:Polyglutamic Acid / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
D004268:DNA-Binding Proteins; C051550:E2 protein, Bovine papillomavirus; D010455:Peptides; D014764:Viral Proteins; D011099:Polyglutamic Acid