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The prompt emission of gamma-ray bursts (GRBs) is widely thought to beradiation from accelerated electrons, but an appreciably larger amount ofenergy could be carried by accelerated protons, particularly if GRBs are thesources of ultra-high-energy cosmic rays (UHECRs). We model the expected photonspectra for such "proton-dominated" GRBs in the internal shock scenario throughMonte Carlo simulations, accounting for various processes related tohigh-energy electrons and protons. Besides proton and muon synchrotroncomponents, emission from photomeson-induced secondary pair cascades becomescrucial, generally enhancing the GeV-TeV and/or eV-keV photons and offering asignature of UHE protons. In some cases, it can overwhelm the primary electroncomponent and result in GRBs peaking in the 10 MeV - 1 GeV range, which may berelevant to some bursts discussed in a recent re-analysis of EGRET TASC data.The dependence of the spectra on key quantities such as the bulk Lorentzfactor, magnetic field and proton-to-electron ratio is nontrivial due to thenonlinear nature of cascading and the interplay of electron- and proton-inducedcomponents. Observations by {\it Fermi}, ground-based telescopes and otherfacilities should test these expectations and provide critical constraints onthe proton acceleration efficiency.

Prompt High-Energy Emission from Proton-Dominated Gamma-Ray Bursts