The HSP70 multigene family consists of several members in eukaryotes. Among
these are BiP, an ER protein, and hsc70, the major constitutively expressed
BiP and hsc70 genes diverged over one billion years ago at about the time
that eukaryotes are presumed to have first appeared. In mammals the amino
acid sequences of both of these proteins are identical or very nearly so
(differences could be due to sequence errors/cloning artifacts).
The mouse and cow proteins are about 650 amino acids long - here are two
examples of long stretches of sequence identifty. Is this the record?
The heat shock inducible proteins, hsp70's, are also highly conserved. The
amino acid sequences of mammalian proteins do not usually differ by more
then one or two substitutions in 650 residues.
I believe that a good case can be made in favor of the argument that the
HSP70 genes are the most highly conserved genes in living organisms.
Laurence A. Moran (Larry)
Dept. of Biochemistry
University of Toronto