A DSA private key is described by this S-expression:
(private-key (dsa (p p-mpi) (q q-mpi) (g g-mpi) (y y-mpi) (x x-mpi)))
DSA prime p.
DSA group order q (which is a prime divisor of p-1).
DSA group generator g.
DSA public key value y = g^x \bmod p.
DSA secret exponent x.
The public key is similar with "private-key" replaced by "public-key" and no x-mpi.