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F. WAYNE OUTTEN , PhD
Assistant Professor, USC College of Arts and Sciences, Chemistry and Biochemistry
DEGREES
B.S., 1995, College of William and Mary
Ph.D., 2001, Northwestern University
Postdoctoral Fellow, 2001-2005, National Institutes of Health
RESEARCH INTERESTS
Research Areas: Microbial metal metabolism, bio-inorganic chemistry, microbial physiology, and microbial genetics; biochemical mechanisms of Fe-S cluster assembly; characterization of transition metal acquisition, trafficking, and storage systems during environmental stress; metal homeostasis during biofilm formation in micro-organisms.
Metal Trafficking and Metal Cofactor Assembly Under Stress Conditions:
My broad research goal is to understand how homeostasis of essential transition metals is maintained in response to environmental stresses. Due to their unique chemical properties, transition metals such as copper, iron, and zinc are critical cofactors in the active sites of enzymes and as structural components in proteins. However, many of these essential metals are toxic when present in excess, indicating a requirement for the cell to maintain a fairly narrow intracellular concentration of each metal. In addition, metal metabolism may be altered by environmental stress through multiple mechanisms. Cells can adjust transport and storage of the metal in response to the stress, either through increased uptake, efflux, or expression of metal storage proteins. The metal or metal cofactor may be directly modified, for instance by oxidation or reduction, leading to a subsequent change in reactivity, ligand affinity, or bioavailability. Conversely, the proteins or other biomolecules that interact with the metal or metal cofactor may themselves be altered by the stress, causing a change in metal metabolism such as release of metal from an active site. Defining the biochemical strategies used by organisms to maintain metal homeostasis under stress will provide insight into critical areas ranging from bacterial pathogenesis to human disease.
The suf pathway and Fe-S cluster assembly under stress:
Fe-S clusters, which contain inorganic sulfur and iron, play key roles in electron transport, as active site cofactors in TCA cycle enzymes, and as exquisite sensors of oxygen and oxygen radicals in stress-responsive transcription factors. However, Fe-S clusters are perturbed by multiple stress conditions. During oxidative stress, superoxide anion (O2•-) can damage 4Fe-4S clusters leading to cluster degradation and release of iron. Therefore, Fe-S clusters are assembled in vivo via intricate biosynthetic pathways. The Fe-S cluster assembly pathway encoded by the sufABCDSE operon is required to assemble Fe-S clusters during iron starvation or oxidative stress, conditions known to disrupt Fe-S clusters in vivo. To determine the biochemical mechanisms used by the suf pathway to achieve this feat, we have purified all six of the suf-encoded proteins. We have found that SufB, SufC and SufD, co-purify as a stable complex. This three-protein complex interacts with the SufE protein to dramatically enhance sulfur donation by the SufS cysteine desulfurase enzyme. SufE acts as a sulfur transfer partner and together with the SufBCD complex, comprises a novel sulfur transfer pathway for Fe-S cluster assembly under stress conditions. Further genetic, regulatory, and biochemical analysis will elucidate how the suf gene products are adapted to acquire iron and sulfur for construction of Fe-S clusters during iron starvation and oxidative stress.
 Metal homeostasis in biofilms:
One nearly universal strategy used by microbes to respond to stress is formation of a complex, three-dimensional structure known as a biofilm. Biofilms occur among microorganisms growing in natural environments and often include multiple species. It is well established that biofilms are highly resistant to environmental stresses, including heavy metal toxicity and oxidative stress. However, the genetic and biochemical mechanisms of biofilm resistance are only partially defined. Understanding metal homeostasis during biofilm formation is critical for understanding biofilm stress resistance and will provide insight into multiple microbial processes. For instance, mixed species biofilms growing on metal surfaces, such as household plumbing or ship hulls, are known to stimulate biocorrosion. In addition, microbial pathogens that form biofilms during infection also encounter metal starvation as they interact with mammalian host cells. Biofilm-specific metal homeostasis systems might be optimized for the microaerobic or nutrient-depleted environments that exist within the biofilm. We are using genetic, biochemical, and cell biology approaches to identify and characterize such systems in order to understand their importance for biofilm physiology.
CONTACT INFORMATION
University of South Carolina
Department of Chemistry and Biochemistry
631 Sumter Street, GSRC 310
Columbia, SC 29208
E-mail
Office: 803 . 777 . 8151 | Fax: 803 . 777 . 9521
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