Purine controlled transcription attenuation in Bacillus subtilis

  • Saxild, Hans Henrik (Project Manager)

    Project Details


    Purines are essential compounds in the metabolism of all cells. They act as components in nucleic acid (DNA and RNA) and are part of cofactors and vitamins. In growing cells of Bacillus subtilis the expression of a number of genes are subjected to purine control among these are pur operon, xpt-pbuX, pbuG, yxjA and ydhL. For pur operon, xpt-pbuX, pbuG and yxjA high concentration of purine in the surrounding medium results in low levels of gene expression. pur operon, xpt-pbuX, pbuG and yxjA are preceded by a long untranslated leader sequence capable of forming mutually exclusive secondary mRNA structures. The former model for the purine controlled transcription attenuation involves the presence of a RNA-binding regulator protein that, under conditions of high purine levels, binds to the so-called antiterminator structure of the leader sequence, which subsequently results in the formation of an alternative structure known as the transcription terminator. By this means the downstream located genes are only transcribed under condition of low purine levels.
    Progress in 1999:
    We have now showed that the ydhL gene, which has a 5´-leader sequence almost similar to the above mentioned purine regulated genes, is regulated in the opposite manner - that means that under high purine conditions the gene expression is stimulated instead of being repressed. YdhL encodes a protein with similarity to efflux pumps and we have shown that YdhL most likely is responsible of pumping excess purine out of the cell. We are now testing the hypothesis that the purine molecules per se can bind to the mRNA molecule and that there is no regulatory protein involved in the attenuation mechanism.
    Effective start/end date01/01/199531/12/1999


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