The natural self-assembly tendency of proteins to build complex structural architectures has kindled inspiration in developing supramolecular structures through the rational design of biomacromolecules. While there has been significant progress in achieving precise control over the morphology of self-assembled structures, combining different molecules within assemblies enables the design of materials with increased complexity, sophisticated structures, and a broad spectrum of functionalities. Here, the development of 1D and 2D peptide–protein coassembled systems based on the design of amphiphilic peptides and engineered proteins is described. The peptide was optimized to form stable self-assembled fibers by evaluating, computationally and experimentally, the assembling tendencies and the supramolecular features of peptides with different lengths and negative charges. A superhelical repeat protein was engineered by fusing one or two amphiphilic peptides into one or both termini. This modification drove the coassembly between the self-assembled fibers and the protein with one or two peptides, resulting in 1D or 2D coassembled systems. The protein films and the 2D coassembled system exhibited high ionic conductivity for a biomolecular system, attributed to their high content of charged residues, positioning these materials as promising candidates for developing bioelectronic devices. Thus, this work provides a versatile framework for developing coassembled materials with tunable dimensionality by using biocompatible building blocks without any additional chemical moieties, highlighting the potential for their use in biocompatible electronics.