IDENTIFICATION AND PURIFICATION OF A FAMILY OF DIMERIC MAJOR COLD SHOCK PROTEIN HOMOLOGS FROM THE PSYCHROTROPHIC BACILLUS-CEREUS WSBC-10201

Whole-cell protein patterns of a psychrotrophic Bacillus cereus strain from cultures grown at 7 and 30 degrees C were compared, This analysi s revealed that at least three major proteins are expressed at a signi ficantly higher rate at 7 degrees C than at 30 degrees C, The most abu ndant of these cold-induced proteins was a small polypeptide of 7.5 kD a, designated CspA, of B, cereus, In addition, four small proteins ver y similar in size to CspA were seen on both 7 degrees C and 30 degrees C two-dimensional protein gels. Immunoblot analysis using B, cereus a nti-CspA antibodies indicated that the five proteins described above p lus an additional sixth protein not visible on silver-stained two-dime nsional gels are members of a B, cereus cold shock protein family, Thi s hypothesis was corroborated by cloning and sequencing of the genes e ncoding five proteins of this family, The protein sequences deduced ar e highly similar and show homology to small procaryotic cold shock pro teins and to the cold shock domain of eucaryotic Y-box proteins, Besid es CspA, only one of the additional five CspA homologs was slightly co ld inducible, In the presence of 100 mM NaCl, the two purified members of the protein family (CspA and CspE) elute as dimers at an apparent molecular mass of 15 kDa from a gel filtration column, At higher salt concentrations, they dissociate into their monomers, Their ability to bind to the ATTGG motif of single-stranded oligonucleotides was demons trated by band shift analysis.