Bayer School of Natural and Environmental Sciences
Peter A. Castric
cold shock proteins, csp genes, E. coli K-12, homologs
E. coli K-12 contains nine csp paralogs, cspA --cspI. Although the csp paralogs are conserved sequences that produce highly similar proteins, expression of each of these genes requires a different means of induction. While cspA, cspB, cspG, and cspI are induced by cold shock, cspC and cspE are constitutively expressed. cspD is induced by stationary phase. The type of induction, if any, needed for cspF and cspH is not known. Studies of CspE have demonstrated that the overexpression of this protein can confer a 10-fold resistance to the DNA decondensing agent, camphor, and upregulates the E. coli rcsA gene by 1.7-fold. Phenotypic assays to determine Csp function show that stablized Csp proteins that are normally degraded by Lon protease (CspC, CspE, CspG, CspI) display resistance to camphor and upregulate the rcsA gene when they are expressed from an arabinose inducible vector harbored in a lon- strain. Csp proteins that are not stabilized (CspA, Csp B, CspF, and CspH), even in the lon- mutant strain, did not display these phenotypes. Csp protein function was further assessed by studying the pattern of Csp protein accumulation across various phases of cell growth. When expression is controlled from an inducible promoter, CspA, CspG, and CspI stability in a lon- strain tends to peak during late log and stationary phase. CspC and CspE stability tends to remain the same throughout each of the growth phases observed, while CspB, CspF, and CspH are not present at all. Overall, my work suggests that CspC, CspE, CspG, and CspI possess similar functions, which they each perform under different environmental conditions and at different phases of cell growth.
Ventrice, C. (2004). Functional Characterization of the csp Homologs of E. coli K-12 (Master's thesis, Duquesne University). Retrieved from https://dsc.duq.edu/etd/1308