Some thoughts on the structural basis of internal imagery.
Apparently, anti-idiotypic antibodies can mimic (almost?) any molecule in an organism or in its environment. If the molecule is a polypeptide, must the variable region of the antibody contain peptide sequences homologous or identical to sequences in the polypeptide it is mimicking? In this article, Bernard Erlanger says 'No', drawing his conclusion mainly, but not solely, from the hemoglobin-myoglobin family of proteins, in which X-ray and sequence data show that identical, functional conformations can be assumed by proteins that differ by as many as 137 of 141 amino acids.
Erlanger
B F
BF
D000595:Amino Acid Sequence; D000906:Antibodies / Q000032:analysis*; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007130:Immunoglobulin Idiotypes / Q000276:immunology*; D009211:Myoglobin / Q000032:analysis; D011487:Protein Conformation; D013329:Structure-Activity Relationship
D000906:Antibodies; D006454:Hemoglobins; D007130:Immunoglobulin Idiotypes; D009211:Myoglobin