FAMILY OF THE MAJOR COLD-SHOCK PROTEIN, CSPA (CS7.4), OF ESCHERICHIA-COLI, WHOSE MEMBERS SHOW A HIGH SEQUENCE SIMILARITY WITH THE EUKARYOTIC Y-BOX BINDING-PROTEINS

The cspA is a gene of Escherichia coli, whose expression is specifical ly induced at low temperatures to a level of 13% of total protein synt hesis. The CspA protein consisting of 70 amino acid residues has high sequence similarity with eukaryotic Y-box DNA-binding proteins. We fou nd two independent clones from the Kohara miniset phage collection, wh ich hybridized with a DNA fragment containing cspA. DNA sequencing of these clones confirmed that the two genes are highly homologous to csp A. One designated cspB is mapped at 35 min on the E. coli chromosome a nd encodes a 71-residue protein with 79% identity to CspA, while the o ther, cspC, is mapped at 40 min and encodes a 69-residue protein with 70% identity. In addition, a DNA sequence upstream of the clpA gene at 19 min published elsewhere contains an open reading frame for a 74-re sidue protein with 45% identity to CspA. All csp genes were fused in t he coding regions with the lacZ gene, and the expression of beta-galac tosidase was examined for these hybrid genes upon cold shock. A simila r cold-shock induction to cspA was observed for cspB but not cspC and cspA These results indicate that E. coli has a family of the cspA gene , some of which are induced by cold shock.