IbpB thermometer | |
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![]() Conserved secondary structure of the IbpB thermometer | |
Identifiers | |
Symbol | ibpB 5' UTR |
Other data | |
RNA type | RNA thermometer |
Domain(s) | E. coli |
PDB structures | PDBe |
The IbpB thermometer is an RNA thermometer element found in the ibpAB operon.[1] The operon contains two heat-shock genes, encoding inclusion body binding proteins A and B (IbpA/B), and is the most drastically upregulated operon under heat-shock in Escherichia coli.[2]
IbpA is regulated by a ROSE element found in its 5' UTR,[3][4] while IbpB has its own heat-sensitive cis-regulatory element. The activity of this thermoregulator was confirmed in vitro but was not found in vivo, suggesting more complicated operon regulation exists in bacterial cells.[1]
The IbpB protein, whose expression is regulated by the IbpB thermometer, is 48% identical to IbpA (at the level of amino acid sequence) yet fulfils a different role in heat shock. When IbpB is absent, IbpA protein will form long fibrils which is unusual for a heat shock protein; IbpB, acting as a co-chaperone, inhibits IbpA from forming this structure.[5]
Under heat shock, IbpB protein dissociates to give two smaller subunits and also rearranges its tertiary structure.[6] This "remarkable conformational transformation"[7] is thought to be essential for IbpB to act as a co-chaperone with IbpA under heat shock.[8]
IbpB has been found to retain active for a significant time after a heat shock stimulus has been removed.[7]