  In brane inflationary scenarios, the cosmological perturbations are supposed
to originate from the vacuum fluctuations of the inflaton field corresponding
to the position of the brane. We show that a significant, and possibly
dominant, contribution to the curvature perturbation is generated at the end of
inflation through the vacuum fluctuations of fields, other than the inflaton,
which are light during the inflationary trajectory and become heavy at the
brane-anti brane annihilation. These fields appear generically in string
compactifications where the background geometry has exact or approximate
isometries and parametrize the internal angular directions of the brane.
