  We propose a five-band tight-binding model for the Fe-As layers of iron
pnictides with the hopping amplitudes calculated within the Slater-Koster
framework. The band structure found in DFT, including the orbital content of
the bands, is well reproduced using only four fitting parameters to determine
all the hopping amplitudes. The model allows to study the changes in the
electronic structure caused by a modification of the angle $\alpha$ formed by
the Fe-As bonds and the Fe-plane and recovers the phenomenology previously
discussed in the literature. We also find that changes in $\alpha$ modify the
shape and orbital content of the Fermi surface sheets.
