Pyruvate-ferredoxin oxidoreductase (PFOR)

Pyruvate-ferredoxin oxidoreductase (PFOR) carries out the central step in oxidative decarboxylation of pyruvate to acetyl-CoA. PFOR from Desulfovibrio vulgaris Hildenborough (DvH) was purified as part of an interdisciplinary project that is developing high-throughput approaches to identify and characterize microbial multi-protein complexes (http://pcap.lbl.gov). We determined the three-dimensional structure of this enzyme by a combination of electron microscopy (EM), single particle image analysis, homology modeling and computational molecular docking (Garczarek et al., J Struct Biol. 2005). Our results show that the DvH PFOR complex is a tetramer of the dimeric form of the related enzyme found in Desulfovibrio africanus (Da), with which it shares a sequence identity of 69%. Docking of a homology model of the DvH PFOR dimer model into our 17 Å resolution EM-reconstruction of DvH PFOR octomers strongly suggests that the difference in oligomerization state for the two species is due to the insertion of a single valine residue (Val383) within a surface loop of the DvH enzyme. This study demonstrates that intermediate resolution EM reconstruction coupled to homology modeling and docking can be powerful enough to infer the functionality of single amino acid residues.