Mutational Analysis Supports Three-Hairpin Model of Attenuator for Transcription Regulation of C Operon in .

The operon in encodes key enzymes for the biosynthesis of branched-chain amino acids (L-isoleucine, L-leucine, and L-valine). This operon has been studied for quite a long time, and it is assumed that three hairpin mRNA structures can be formed in its regulatory region; however, their functionality and role in the attenuation mechanism of the operon are not completely clear. In the present work, we performed a mutational analysis of mRNA secondary structures in the regulatory region of the operon, which allowed us to propose a model of the regulation of its transcription involving three mRNA hairpins that essentially act as a transcription terminator, an antiterminator, and an antiantiterminator.

Identification of hox genes and analysis of their transcription in the unicellular cyanobacterium Gloeocapsa alpicola CALU 743 growing under nitrate-limiting conditions.

The unicellular non-N(2)-fixing cyanobacterium Gloeocapsa alpicola CALU 743 contains a bidirectional hydrogenase. Parts of all structural genes, encoding the hydrogenase, were identified, cloned and sequenced. When comparing the sequences with analogous sequences from other cyanobacteria the highest similarity was observed with hox genes from Synechocystis sp.