Review: What can structural classifications reveal about protein evolution?

In this article we present a review of the methods used for comparing and c lassifying protein structures. We discuss the hierarchies and populations o f fold groups and evolutionary families in some of the major classification s and we consider some of the problems confronting any general analyses of structural evolution in protein families. We also review some more recent a nalyses that have expanded these classifications by identifying sequence re latives in the genomes and thereby reveal interesting trends in fold usage and recurrence. (C) 2001 Academic Press.