Consistent with our recent findings of transcriptional regulation of cspA by CspE, we have identified a motif identical to the CspE consensus. CspE and CspB have Kd values in the range 0.23-0.9 x 10(-6) M, while CspC has 10-fold lower binding affinity. The consensus sequences for CspB, CspC and CspE are U/T stretches, AGGGAGGGA and AU/AT-rich regions, especially AAAUUU, respectively.
In the present study, we show that these proteins are able to bind preferentially to specific RNA/single-stranded DNA sequences. As a step towards identification of the target genes of Csp proteins, we investigated the RNA binding specificities of CspB, CspC and CspE by an in vitro selection approach (SELEX). The cellular functions of other Csp proteins are yet to be fully elucidated, and their sequence specific binding capabilities have not been identified. This is considered to be important for its proposed function as an RNA chaperone to prevent the formation of secondary structures in RNA molecules, thus facilitating translation at low temperature.
CspA, the major cold shock protein, binds RNA with low sequence specificity and low binding affinity.
The CspA family of Escherichia coli comprises nine homologous proteins, CspA to CspI.
