How to import a X509 cert into gpg?

[Song Yi]

Hi,
    I can import the X509 cert into PGP6.5.8 on windows. Can I import it
into GPG on Linux?

    I have tried to export it again from PGP6.5.8, make a pgp form .asc
file, and transfer it to Linux, then run gpg --import key.file, it failed:
    gpg: signature packet without keyid
    gpg: key DA326647: no valid user IDs
    gpg: this may be caused by a missing self-signature
    gpg: Total number processed: 1
    gpg:           w/o user IDs: 1

    Then, how can I import the x509 cert into gpg?