Transformations of Dimethylsulfide - The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment - page 297

Figure 8 Alignments of amino acid sequences of Type II (a, b) and Type III (b)DMSOreductase
family enzymes comparing the position of the putative amino acid ligand to the Mo center of DmsA
DMSO reductases relative to other enzymes of the same type. Panel a: alignment of Type II DMSO
reductase family enzyme, Panel b: alignment of Type II and Type III DMSO reductase family
enzymes. The alignments only show the regions around the amino acid ligands to the Mo center
present in these enzymes. The Mo-ligating amino acids are highlighted: grey - aspartate ligands
typical of Type II enzymes; white - serine ligands typical of Type III enzymes. DH, dehydrogenase;
red, reductase; SerA, selenite reductase; ClrA, chlorate reductase; DMSDH, DMS dehydrogenase;
BisC, biotinsulfoxide reductase; DmsA, Dms-type DMSO reductase; DorA, Dor-type DMSO
reductase; TorA, trimethylamine oxide reductase; TorZ, S- and N-oxide reductase.
for DmsA proteins from E. coli, H. influenzae ,and Halobacterium NRC-1 (Figure 8 ),
the aspartate Mo ligands of the non-DmsA sequences can be easily identified, but
within the DmsA sequence group neither the DmsA-Ser176 residue nor the aspartate
residue of the 'GDYS' motif align with the other aspartate residues. The DmsA
aspartate residues of the 'GDYS' motif align with each other approximately 5 amino
acids upstream of the conserved Type II enzyme aspartate residue, and it becomes
obvious that an equivalent of the DmsA-Ser176 residue is not present in the
Halobacterium NRC-1 DmsA sequence, confirming the predictions of [ 174 ].
So together this suggests that unlike the Dor-type DMSO reductases, DmsA-type
DMSO reductases might indeed possess an aspartate ligand to the Mo center, and
that the effects observed in the DmsA-Ser176 mutants of E. coli might be caused by
the close proximity of this residue to the Mo center. Mutation of this residue could
lead to perturbations of the protein backbone and the side chain packing which
could explain the effects of such mutations on the properties of the DmsA Mo
center reported by [ 148 ].