Electrochemical Properties of Stellacyanin as Probed by Site-Directed Mutagenesis
Noah Stites-Hallett and Elena Hunanyan
Faculty Advisor: M. Hill and R. Hardy

      It has been observed in azurin [1], plastocyanin, and stellacyanin (unpublished work) that a redox potential shift occurs when these proteins are exposed to non-denaturing concentrations of GuHCl. This shift is caused by a GuHCl-protein complex that interrupts the secondary and/or tertiary structures surrounding the Cu²⁺ ion. This disruption seems to cause these proteins to conform to a common redox potential. We are currently examining this phenomenon with respect to stellacyanin in an effort to determine if this default redox potential is common throughout the entire cupredoxin family. We are additionally utilizing site directed mutagenesis to probe the Cu²⁺ coordinating ligands as well as a tryptophan residue (uniquely conserved in all blue copper proteins) in the stellacyanin sequence. Investigation into this occurrence will help us to understand how electron transfer enzymes are regulated and how subtle structural altercations are able to drastically change electrochemical thermodynamics within a specific class of redox-active proteins.

     Reference: [1] Wittung-Stafshede, Pernilla et all. High-potential states of blue and purple copper proteins. Biochimica et Biophysica Acta. 1998; 437-443

Support provided by: NSF-AIRE, NIH, Packard Foundation, Ford Foundation