This superfamily entry consists of the C-terminal domain of the ribosomal protein L7/L12 from the large (50S) subunit of the prokaryotic ribosome, and the adaptor protein ClpS. Structurally this domain adopts an alpha/beta sandwich topology and consists of three alpha-helices connected to three antiparallel beta-strands. The protein has a globular shape, with a curved layer of three antiparallel alpha-helices over a twisted antiparallel beta-sheet. Dimerisation of ClpS and L7/L12 was suggested to occur through the N-terminal domain. This short extended N-terminal region in ClpS is followed by the central seven-residue beta-strand, which is flanked by two other beta-strands in a small beta-sheet.

The L8 protein complex consisting of ribosomal proteins L7/L12 and L10 in E. coli is assembled on the conserved region of 23 S rRNA termed the GTPase-associated domain. L7/L12 occur in four copies organised as two dimers. The L7/L12 dimer probably interacts with EF-Tu. L7 and L12 have identical sequences except an N-terminal serine in L7 which is post-translationally modified (addition of an acetyl group). The eukaryotic counterpart of the prokaryotic L8 is the P 'complex' consisting of homodimers of P1 and P2 and monomeric P0.

In the bacterial cytosol, ATP-dependent protein degradation is performed by several different chaperone-protease pairs, including ClpAP. The N-end rule targets specific proteins for destruction in prokaryotes and eukaryotes. ClpS is an N-end rule adaptor, which recognises N-end rule substrates, tethers them to the ClpAP protease, and then actively transfers the substrate to ClpAP for degradation. ClpS directly influences the ClpAP machine by binding to the N-terminal domain of the chaperone ClpA. The degradation of ClpAP substrates, both SsrA-tagged proteins and ClpA itself, is specifically inhibited by ClpS. ClpS modifies ClpA substrate specificity, potentially redirecting degradation by ClpAP toward aggregated proteins.

PFAM:PF00542, PFAM:PF02617, INTERPRO:IPR014719, INTERPRO:IPR003769,PMID:3309338,PMID:10488095,PMID:12235156,PMID:11931773,PMID:18995838