proteins with 30% homology should have the same general fold: reference for this ?

[Ng]

     There's probably an older reference than this, but you may want to
look at

Sander C, Schneider R. Database of homology-derived protein structures and
the structural meaning of sequence alignment. Proteins 1991, 9:56-58.


For a very recent critical reassessment of using sequence identity as
a measure of homology, see


Brenner, SE; Chothia, C; Hubbard, TJP.
     Assessing sequence comparison methods with reliable structurally
   identified distant evolutionary relationships.
     PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF
   AMERICA, 1998 MAY 26, V95 N11:6073-6078.


-- 
Ho Leung Ng
holeung at ucla.edu