We address the problem of charge transfer (CT) between a nanosized inorganic system and a protein from a theoretical and numerical perspective. The CT process is described on an atomistic level by applying an electronic Hamiltonian that takes into account the chemical bond, vibronic coupling effects, and polarization degrees of freedom. As a structurally well-characterized example, we consider a complex of C-60 and its antibody. For this system, we find a novel efficient protein CT mechanism; through-space superexchange is mediated by stacked pi orbital systems. The predicted rates are comparable to those obtained for short-range electron tunneling through covalent bonds, the fastest ground-state CT process known for proteins.