Wednesday, June 17, 2015

518 - Cloning, sequencing and characterization of the [NiFe]hydrogenase-encoding structural genes (hoxK and hoxG) from Azotobacter vinelandii

To continue our journey back in time through the discovery of the uptake hydrogenase genetics in Azotobacter vinelandii, this study describes the sequencing of the hydrogenase structural genes, hoxKG.

What They Saw
They probed A. vinelandii DNA with a chunk from A. chroococcum with its hydrogenase genes, and sequenced a fragment they found. This fragment contained three full open reading frames (ORFs) and possibly the beginning of a fourth. The first two encode the structural subunits, HoxK and HoxG (for hydrogen oxidation), based on comparison to sequences in other organisms.

HoxK seems to undergo some processing, since the final protein is smaller than that predicted by the gene sequence; there might be a signal sequence that localizes the protein to the membrane or something. The structural ORFs overlap each other a little, indicating that they're probably transcribed as a unit (in the same operon) which helps the proportions come out right.

The third ORF, ORF3 (which we know now is hoxZ) was also similar to other organisms, and seemed to be a membrane protein of some sort. Possibly part of the hydrogenase electron transport chain.


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