  Rotational friction on proteins and macromolecules is known to derive
contributions from at least two distinct sources -- hydrodynamic (due to
viscosity) and dielectric friction (due to polar interactions). In the existing
theoretical approaches, the effect of the latter is taken into account in an
{\it ad hoc} manner, by increasing the size of the protein with the addition of
a hydration layer. Here we calculate the rotational dielectric friction on a
protein ($\zeta_{DF}$) by using a generalized arbitrary charge distribution
model (where the charges are obtained from quantum chemical calculation) and
the hydrodynamic friction with stick boundary condition,
($\zeta_{hyd}^{stick}$) by using the sophisticated theoretical technique known
as tri-axial ellipsoidal method, formulated by Harding [S. E. Harding, Comp.
Biol. Med. {\bf 12}, 75 (1982)]. The calculation of hydrodynamic friction is
done with only the dry volume of the protein (no hydration layer). We find that
the total friction obtained by summing up $\zeta_{DF}$ and
$\zeta_{hyd}^{stick}$ gives reasonable agreement with the experimental results,
i.e., $\zeta_{exp} \approx \zeta_{DF} + \zeta_{hyd}^{stick}$.
