Simply put,if if you are thinking of “being"being in the proton”proton" as simply having a ghostly appearance in the form of loop diagrams with processes like γ —> e^± $\gamma\to e^\pm$,sure sure nothing prevents such a thing.But But you'll never really get real asymptotic states of electrons unless it's a βbeta plus decaydecay where protons can convert into neutrons (well technically they emit positrons but you get the gist).