"The origin and evolution of protein superfamilies.
The organization of proteins into superfamilies based primarily on their sequences is introduced: examples are given of the methods used to cluster the related sequences and to elucidate the evolutionary history of the corresponding genes within each superfamily. Within the framework of this organization, the amount of sequence information currently and potentially available in all living forms can be discussed. The 116 superfamilies already sampled reflect possibly 10% of the total number. There are related proteins from many species in all of these superfamilies, suggesting that the origin of a new superfamily is rare indeed. The proteins so far sequenced are so rigorously conserved by the evolutionary process that we would expect to recognize as related descendants of any protein found in the ancestral vertebrate. The evolutionary history of the thyrotropin-gonadotropin beta chain superfamily is discussed in detail as an example. Some proteins are so constrained in structure that related forms can be recognized in prokaryotes and eukaryotes. Evolution in these superfamilies can be traced back close to the origin of life itself. From the evolutionary tree of the c-type cytochromes the identity of the prokaryote types involved in the symbiotic origin of mitochondria and chloroplasts begins to emerge."
I don't have access to the whole paper, unfortunately, but it should interest TB.
------------------ Occam's razor is not for shaving with.
^ This paper (from 1976 BTW) is one of the seminal papers identifying the superfamilies. Dayhoff is a famous seqeunce analysis guy who I cite in my lectures.
Superfamilies have conserved 3D structres and frequently little or no seqeunce similarity that is conserved across the family.
The statements made in this abstract are supersitions that presume evolution.
It does not discuss the acual origin of each family but the evolution within the families! Most papers on 'origin of families' are misleading entitled - they are talking about how the families spread out from a parent gene.
Gene families themselves are subsets of superfamiles or are at the superfamily level themselves. Families within superfamilies may or may not be convergent from an evolutionary POV.
[This message has been edited by Tranquility Base, 10-08-2002]