1)      E. coli requires nickel for three NiFe-hydrogenases that catalyze the reversible oxidation of hydrogen. High concentration of Ni(II) can be toxic to the cell and therefore has to be tightly regulated. RcnR is a 40 kDa homotetrameric transcriptional repressor that binds to DNA in the apo form and releases DNA in response to the binding Co(II) or Ni(II) resulting in the expression of the exporter RcnA and a periplasmic protein associated with export, RcnB. RcnR binds to a variety of first-row transition metals in vitro. Despite binding the first row transition metals, lacZ reporter assays determined that only the binding of Ni(II) or Co(II) results in the de-repression of rcnA. The results from this work suggest that there are two protein conformations that lead to DNA release one that features a M-S distance at 2.3 � as seen for Co(II)-WT RcnR, and another with M-S distance at 2.6 � that is typical for Ni(II) WT-RcnR. XAS and lacZ studies suggest that as long as either conformation is maintained when metal binds then the metal binding will result in the expression of RcnA.2)      S. aureus has a unique sulfur metabolism pathway as it cannot utilize sulfate as a sulfur source but can grow on thiosulfate and sulfide. The cst operon was recently discovered in S. aureus and may be involved in sulfur assimilation, sulfur trafficking and/or sulfide detoxification. This work focuses on CstA, a putative sulfur transferase that may be involved in the shuttling of sulfur as cysteine persulfides to downstream targets. NMR studies reveal that C66 and C128 are within disulfide bonding distance, consistent with a persulfide shuttling model and the TusA and RHOD domains pack against one another.

Importance of Ni(II) to <i>E. coli</i> and sulfur to <i>S. aureus</i>

246th National Meeting (2013)

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Importance of Ni(II) to E. coli and sulfur to S. aureus