CYTOCHROME C(550) EXPRESSION IN PARACOCCUS-DENITRIFICANS STRONGLY DEPENDS ON GROWTH CONDITION - IDENTIFICATION OF PROMOTER REGION FOR CYCA BY TRANSCRIPTION START ANALYSIS

The periplasmic cytochrome c(550) content of Paracoccus denitrificans has been shown by immunological detection to be strongly dependent on the mode of growth. Cells grown under anaerobic, denitrifying conditio ns or methylotrophically in the presence of oxygen contained substanti ally more cytochrome c(550) than cells grown aerobically on multicarbo n substrates. A similar pattern was observed when expression of the cy cA gene (encoding cytochrome c(550)), was monitored using an Escherich ia coli alkaline phosphatase gene (phoA) fusion as a reporter of cycA promoter activity. The increase in cycA expression observed during gro wth on C-1 substrates was substantially diminished if succinate was al so present. These results reveal that expression of cycA is subject to multiple regulatory controls and suggest that cytochrome c(550) has a general role in electron transfer to periplasmic reductases required for anaerobic denitrifying growth and from dehydrogenases required for aerobic growth on C-1 compounds, Two major transcriptional initiation start points for the cycA gene have been identified.