Stringent starvation protein B (IPR007481)

Short name: SspB

Overlapping homologous superfamilies

Family relationships



Escherichia coli stringent starvation protein B (SspB), is thought to enhance the specificity of degradation of tmRNA-tagged proteins by the ClpXP protease. The tmRNA tag, also known as ssrA, is an 11-aa peptide added to the C terminus of proteins stalled during translation, targets proteins for degradation by ClpXP and ClpAP. SspB is a cytoplasmic protein that specifically binds to residues 1-4 and 7 of the tag. Binding of SspB enhances degradation of tagged proteins by ClpX, and masks sequence elements important for ClpA interactions, inhibiting degradation by ClpA [PMID: 11535833]. However, more recent work has cast doubt on the importance of SspB in wild-type cells [PMID: 11810257]. SspB is encoded in an operon whose synthesis is stimulated by carbon, amino acid, and phosphate starvation. SspB may play a special role during nutrient stress, for example by ensuring rapid degradation of the products of stalled translation, without causing a global increase in degradation of all ClpXP substrates [PMID: 11009422].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.