2 OPEN READING FRAMES (ORFS) IDENTIFIED NEAR THE HYDROGENASE STRUCTURAL GENES IN AZOTOBACTER-VINELANDII, THE 1ST ORF MAY ENCODE FOR A POLYPEPTIDE SIMILAR TO RUBREDOXINS

Sequencing of 744 base pairs (bp) of a cloned section of DNA from Azotobacter vinelandii reveals two complete, closely-spaced open reading frames (ORF1 and ORF2). Both ORFs are transcribed from the same DNA strand as that of the structural genes for hydrogenase (hoxK and hoxG, Menon, A.L. et al. (1990) Gene 96, 67-74), and are located downstream from the latter genes. The distance between the end of hoxG and the beginning of ORF1 is approx. 3.0 kilobases (kb). Most of the deduced amino acid sequence of ORF1 shares high homology with rubredoxin sequences. Some of the deduced amino acid sequence of ORF2 shares homology with that of a reported partial ORF from Rhodobacter capsulatus, ORF located within a region of DNA required for dihydrogen oxidation in that organism. Implications of these findings with respect to dihydrogen metabolism are discussed.