  We show that the K-K spectrum of IIB string on AdS_5 x S_5 is described by
``twisted chiral'' N=4 superfields, naturally described in ``harmonic
superspace'', obtained by taking suitable gauge singlets polynomials of the
D3-brane boundary SU(n) superconformal field theory. To each p-order polynomial
is associated a massive K-K short representation with 256 x 1/12 p^2(p^2 -1)
states. The p=2 quadratic polynomial corresponds to the ``supercurrent
multiplet'' describing the ``massless'' bulk graviton multiplet.
