Carboxy-terminal determinants of intracellular protein degradation.

Abstract

Using the amino-terminal domain of k repressor as a model system, we show that residues in an unstructured region at the extreme carboxyl terminus of the protein are important for determining its proteolytic susceptibility in Escherichia coil Nonpolar amino acids are destabilizing when placed at the 5 carboxy-terminal residue positions, whereas charged and polar residues are stabilizing. The stabilizing effect of a single charged residue is greatest when it is at the terminal position and diminishes with increasing distance from the carboxyl terminus. The position of destabilizing sequences with respect to the free carboxyl terminus is important for their effect, but their distance from the folded portion of the protein is not important. Specific degradation of proteins with nonpolar carboxyl termini has been reconstituted in vitro using a partially pure, soluble fraction. This degradation is not ATP-dependent. Moreover, amino-terminal domain variants with nonpolar carboxyterminal residues are still rapidly degraded in strains that are deficient in proteolysis of abnormal proteins. These data suggest that the degradation of amino-terminal domain variants with nonpolar carboxy-terminal residues involves proteolytic components distinct from those known to be important for the turnover of unfolded proteins in E. coil

P22 Arc repressor: Enhanced expression of unstable mutants by addition of polar C‐terminal sequences

“…Two factors, thermodynamic stability and C-terminal sequence, appear to determine the susceptibility of Arc and its variants to intracellular degradation (Vershon et al, 1986;Bowie & Sauer, 1989b;Parsell & Sauer, 1989;Parsell et al, 1990). Protein stability is thought to be impor- tant because many mutations that reduce thermodynamic stability also lead to increased degradation in the cell.…”

Functional Significance of an Evolutionarily Conserved Alanine (GCA) Resume Codon in tmRNA in Escherichia coli

“…Thus, the process of trans-translation in E. coli appends AANDENYALAA sequence to the incomplete polypeptide and marks it for degradation by cellular proteases. The C-terminal amino acids in the appended sequence are important for recognition by the cellular proteases; and while the tmRNA mutants that encode ANDENYALDD or ANDEHHHHHH rescue the stalled ribosomes, they do not direct the tagged proteins to degradation (9,11,17,25). Interestingly, the first amino acid (Ala) of the short peptide encoded by the resume codon GCN is evolutionarily conserved across the tmRNA sequences from different species.…”

Degradation of C-terminal tag sequences on domain antibodies purified fromE. colisupernatant

“…The degradation was, however, only reduced and not completely eliminated, which is not surprising as a wide range of other proteases both cytoplasmic and periplasmic exists in E. coli. 21 c There are several other proteases that recognizes their substrates based on the composition of the carboxy terminus, and the location of especially non-polar residues has been linked to the susceptibility of proteolysis of proteins in E. coli 40 c…”