  It has been shown recently that the problem of rapid proton decay induced by
dimension five operators arising from the exchange of colored Higgsinos can be
simply avoided in grand unified models where a fifth spatial dimension is
compactified on an orbifold. Here we demonstrate that this idea can be used to
solve the Higgsino-mediated proton decay problem in any realistic SO(10) model
by lifting that model to five dimensions. A particular SO(10) model that has
been proposed to explain the pattern of quark and lepton masses and mixings is
used as an example. The idea is to break the SO(10) down to the Pati-Salam
symmetry by the orbifold boundary conditions. The entire four-dimensional
SO(10) model is placed on the physical SO(10) brane except for the gauge
fields, the 45 and a single 10 of Higgs fields, which are placed in the
five-dimensional bulk. The structure of the Higgs superpotential can be
somewhat simplified in doing so, while the Yukawa superpotential and mass
matrices derived from it remain essentially unaltered.
