Experimental explorations of functional mechanisms in natural electron-transfer proteins are often frustrated by their fragility and extreme complexity. We have designed and synthesized four-alpha-helix-bundle redox proteins, maquettes, that are much simplified and more robust than natural redox. proteins and can be designed to bind onto electrode surfaces to facilitate systematic investigations. The points of interest that can be now assessed are not only the processes that govern biological assembly of equilibrium structures, electrochemistry, and electron tunneling rates but also how these factors are coupled together to effect redox driven catalysis. Here we describe maquettes that bis-histidine ligate protoporphyrin IX (heme), much like native b cytochromes, as well as contain charged surface patches, much like native cytochrome c. The positively charged residues aid adsorption to negatively charged surfaces, such as gold electrodes modified by 11-mercaptoundecanoic acid, and facilitate cyclic voltammetry (CV) measurements. CV demonstrates the reversible electrochemistry typical for cytochrome b as well as the coupling of the b-heme oxidation and reduction to proton exchange. The pH dependency of redox midpoint potentials reveals a major (three pH units) shift of the pK(a) which matches the shift previously shown to originate in nearby glutamates(1). The redox potentials correspondingly shift from -0.24 (pH > pK(red), deprotonated) to -0.11 V (pH < pK(ox), protonated). The rate of electron transfer at zero driving force between the hemes and the gold electrode was determined to be 120 s(-1), a rate consistent with tunneling through the mercaptoundecanoic acid spacer and suggesting that the coupled proton exchange is not rate limiting. Reduction of the heme in the presence of CO-saturated buffer shifted the oxidation peak from -0.2 to +0.35 V, indicating massive preferential CO binding to the reduced heme. Consistent with solution spectroscopy, CO must displace one axial histidine to the heme to form the His-CO form of the ferrous heme. The CO is released upon heme oxidation at high potentials. In contrast to coupled proton exchange, CO binding/release and ligand exchange are slow on the time scale of electron tunneling between the heme edge and the electrode.