Protein structure databases?

[CC]

Hi --
      Do there exist databases that have information about the secondary
structure, active sites, mutations that disrupt function, etc. of
evolutionarily conserved proteins?  I am particularly looking for
information on subunits of ATP synthase FO and cytochrome c oxicase, as
well as other H+ membrane pore-forming comlexes.  Any information would be
greatly appreciated -- please send e-mail to cc37 at cornell.edu.  Sorry if
this is a FAQ, but I couldn't find the archive.
      Thanks!
                                               -- CC