FIG. 1.

Role of the gapB promoter region in PGK protein production. (A) The gapB-pgk-fda gene cluster. Positions of the oligonucleotides OGB1, OGB3, OGB5, and OGB6 used for PCR amplification of the gapB and pgk genes are represented by horizontal arrows. The gapB upstream region is represented in black and the gapB and pgk coding regions are shown in white and grey, respectively. The intergenic regions between gapB and pgk and between pgk and fda are striped. (B) Fragments cloned in the plasmids used to analyze pgk gene expression. Construction of plasmids pPBK500 and pBK200 is described in Materials and Methods. Cells transformed with the plasmids pPBK500 and pBK200 were grown in M63 medium supplemented with glucose in the presence of ampicillin at 37°C until stationary growth phase. After sonication, PGK activity was measured in the soluble fraction as described in Materials and Methods. Specific activities were expressed in nanomoles of NADH per minute per OD₂₈₀ unit per OD₆₀₀ unit at which cells were harvested. The ratio of the specific activities (sp act [pPBK500/pBK200]) is the average value of the ratios determined for three different cultures.