A non-cold-inducible cold shock protein homolog mainly contributes to translational control under optimal growth conditions

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Abstract

Cold shock proteins (Csps) include both cold-induced and non-cold-induced proteins, contrary to their name. Cold-induced Csps are well studied; they function in cold acclimation by controlling transcription and translation. Some Csps have been reported to contribute to other cellular processes. However, the functions of non-cold-induced Csps under optimal growth conditions remain unknown. To elucidate these functions, we used transcriptome and proteome analyses as comprehensive approaches and have compared the outputs of wild-type and non-cold-induced Csp-deletion mutant cells. As a model organism, we selected Thermus thermophilus HB8 because it has only two csp genes (ttcsp1 and ttcsp2); ttCsp1 is the only non-cold-induced Csp. Surprisingly, the amount of transcripts and proteins upon deletion of the ttcsp1 gene was quite different. DNA microarray analysis revealed that the deletion of ttcsp1 did not affect the amount of transcripts, although the ttcsp1 gene was constantly expressed in the wild-type cell. Nonetheless, proteomic analysis revealed that the expression levels of many proteins were significantly altered when ttcsp1 was deleted. These results suggest that ttCsp1 functions in translation independent of transcription. Furthermore, ttCsp1 is involved in both the stimulation and inhibition of translation of specific proteins. Here, we have determined the crystal structure of ttCsp1 at 1.65 Å. This is the first report to present the structure of a non-cold-inducible cold shock protein. We also report the nucleotide binding affinity of ttCsp1. Finally, we discuss the functions of non-cold-induced Csps and propose how they modulate the levels of specific proteins to suit the prevailing environmental conditions.

Database

Structural data are available in the Protein Data Bank databases under the accession number

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