Bacteriophage Mu repressor as a target for the Escherichia coli ATP-dependent Clp Protease.

Abstract

Bacteriophage Mu repressor, which is stable in its wildtype form, can mutate to become sensitive to its Escherichia coli host ATP‐dependent ClpXP protease. We further investigated the determinants of the mutant repressor's sensitivity to Clp. We show the crucial importance of a C‐terminal, seven amino acid long sequence in which a single change is sufficient to decrease the rate of degradation of the protein. The sequence was fused at the C‐terminal end of the CcdB and CcdA proteins encoded by plasmid F. CcdB, which is naturally stable, was unaffected, while CcdA, which is normally degraded by the Lon protease, became a substrate for ClpXP while remaining a substrate for Lon. In agreement with the current hypothesis on the mechanism of recognition of their substrates by energy‐ dependent proteases, these results support the existence, on the substrate polypeptides, of separate motifs responsible for recognition and cleavage by the protease.

Versatile Action of Escherichia coli ClpXP as Protease or Molecular Chaperone for Bacteriophage Mu Transposition

“…Wawrzynow et al (42) have hypothesized that determinants on the substrate specify whether ClpX will release the substrate to promote protein folding or present the substrate to ClpP for degradation. Determinants necessary for degradation are present in the C-terminal regions of the ClpXP substrates MuA (28,41) and Mu Vir repressor (43). The last 10 amino acids at the C terminus of MuA, when attached to the C terminus of the phage P22 Arc protein, are sufficient to convert Arc into a ClpXP substrate (41).…”

“…The last 10 amino acids at the C terminus of MuA, when attached to the C terminus of the phage P22 Arc protein, are sufficient to convert Arc into a ClpXP substrate (41). However, when 7 amino acids from the C terminus of Vir3061 are fused to F plasmid proteins CcdA and CcdB, only CcdA becomes a ClpXP substrate (43). This leaves open the possibility that additional determinants present in Arc and CcdA but not in CcdB are also needed to promote degradation of the substrate by the protease.…”

The tRNA function of SsrA contributes to controlling repression of bacteriophage Mu prophage

“…Mu repressor is also a target of this protease (7,9), and SsrA is essential for the thermal induction of Mucts62 (29). To elucidate the mechanism by which SsrA affects the physiology of Mu, and in particular the key regulator of the lysis-lysogeny decision, Repc, we have studied the effect of different ssrA alleles on prophage induction and on the physical properties of the repressor.…”

“…Muvir repressors carry a frameshift mutation that alters the C terminus end of Repc, making the protein hypersensitive to degradation by the host ATP-dependent protease ClpXP. This property is transmitted to the more stable wild-type (WT) and cts repressors, enabling Muvir phages to induce the resident prophage on superinfection of a WT Muc ϩ or Mucts lysogen (4)(5)(6)(7)(8)(9). Four point mutations in the N-terminal part of Repc (cts45:S18L; cts71:M28I; cts25:D43G; and cts62:R47Q) (Fig.…”

Proteasomes in the archaea from structure to function

“…N-terminal domains including destabilizing residues of the N-end rule also specifically target proteins for degradation by the proteases such as ClpP of E. coli (218,244). Proteins with destabilizing nonpolar C-termini are recognized by Clp and FtsH proteins in E. coli (245)(246)(247)(248)(249)(250). This includes the ssrA-tagging system which adds nonpolar C-termini to damaged proteins produced from 3'-truncated mRNA (251), mRNAs which contain rare codons, and during tRNA scarcity (252).…”