The hydrogen atom gets the spectrum it has because you analyze the Schrodinger equation in spherical symmetry with the potential given by $V=-\frac{1}{4\pi\epsilon_0}\frac{e^2}{r}$. Yet the same potential term can be given by 2 masses in a gravitational field, where you replace the charges with masses and the constant also changes.
Consider if we want to achieve an orbit radius equal to the Bohr radius. In that case, we need to make sure that the mass of the nucleus is corrected such that
$$GM_n*m_e=\frac{1}{4\pi\epsilon_0}e^2$$
Doing that calculation you get a mass of the nucleus of about 2.08e9kg. Using the formula for the Schwarzchild radius you get that this corresponds to a black hole with radius 3.01e-18m. So that is much smaller than the dimensions of a usual nucleus but that is not a major problem (or at least I think so)
Would such a gravitationally bound "hydrogen" atom be possible or are there other variables which play a role and make this configuration unstable?