An exact approach is introduced to establish and compare quantitative structure-function relationships in electron transfer proteins. The strategy is based on the idea of an electron transfer contact map and is motivated by reduced descriptions of 3D protein structure that emphasize the folded conformation (ribbon drawings, distance contact maps, and Ramachandran plots). Electron transfer contact maps render the protein-mediated electronic coupling information in a compact and transferable form. The method includes all contributions of multiple interfering tunneling pathways to the tunneling propagation and can be implemented at many levels of electronic structure theory. Contact maps are used to interpret the influence of mutations on electronic propagation in model peptides.