ABSTRACT
The three-dimensional structure of a protein is critical for a complete understanding of its biochemical function. Structural genomics projects aim to determine three-dimensional protein structures on a genome-wide scale. Protein function is a somewhat vague term in that it may be described at a variety of levels from biochemical through to phenotypic function. Homologous superfamilies provide evidence for multiple gene duplication events, and these may be the predominant source of new gene functions. Genome sequencing projects have driven the development of functional classification schemes. Most functional classification schemes are hierarchical or tree-like in nature. Few schemes address the multidimensionality of protein function and instead they mix the 'apples and oranges' of function. The chapter outlines the functional information that can be derived from a protein structure itself and from the structural relationships it may share with other proteins of known fold. Protein Databank (PDB)sum is a Web-based database that provides detailed information on every protein in the PDB.
