Investigations of the Efficient Electrocatalytic Interconversions of Carbon Dioxide and Carbon Monoxide by Nickel-Containing Carbon Monoxide Dehydrogenases - The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment - page 73

Figure 2 3D-structures of carbon monoxide dehydrogenases that have been studied by protein film
electrochemistry. Upper left:CODHII Ch (PDB code 3B53) showing how a relay of FeS clusters
leads from the exposed D-cluster (black) to two C-clusters, each one housed in one of the subunits.
Lower left: Same structure viewed facing up from the D-cluster. Right:CODH/ACS(PDBcode
2Z8Y) shown with the CODH viewed in same way as for lower-left view of CODH II Ch .
Of the remaining examples, CODH IV Ch is suggested to be associated with a
multisubunit enzyme complex for oxidative stress response based on genomic
analysis, while the biological role of CODH V Ch remains unclear.
The ease by which these enzymes interconvert CO 2 and CO has attracted intense
interest from both chemists and biochemists, who have applied a variety of spec-
troscopic and structural methods in efforts to establish a firm mechanistic under-
standing. The aim of this chapter is to describe how the application of protein film
electrochemistry (PFE) has added to this understanding [ 17 - 19 ]. But first we will
summarize some of the structural and spectroscopic information that has been
available now for several years.
2 Nickel-Containing Carbon Monoxide Dehydrogenases
Several crystal structures of NiFe-containing CODH (Class IV) or CODH/ACS
(Class III) from different organisms have been solved [ 4 , 8 , 15 , 20 - 22 ]. All Class
IV enzymes have a dimeric structure (Figure 2 ) in which each monomer contains a