Cloning and regulatory analysis of groESL operon from halophilic lactic acid bacterium Tetragenococcus halophila

The groESL operon of a halophilic lactic acid bacterium, Tetragenococcus halophila, was cloned and sequenced. The nucleotide sequence of 2,853-bp revealed the presence of two open reading frames corresponding to the groES and groEL genes. The molecular masses of GroES and GroEL proteins were calculated to be 10,153 and 56,893 Da, respectively. They showed high similarities with the corresponding proteins of other lactic acid bacteria such as Lactobacillus zeae. CIRCE (Controlling Inverted Repeat of Chaperone Expression) element was identified in the upstream region of groES. Northern blot hybridization has demonstrated that the groES and groEL genes are transcribed as a bicistronic mRNA of 2.2 kb, and transcriptionally induced 3.8-fold by heat shock (45 °C) for 30 min. The amount of groESL mRNA was also increased about 4-fold by high NaCl condition. Primer extension analysis indicated that the expression of T. halophila groESL was governed by the constitutive promoter both under normal and stress conditions.