Enzymes of nucleotide synthesis.

Seven new structures reported during the past year have increased dramatically our understanding of enzymes involved in nucleotide de novo synthesis and salvage. Several new protein folds have been identified, including at least four prototypes for new functional families. The construction of larger structures from modules with a catalytic function is a recurring theme. Our understanding of the structural basis of allostery will be enriched by the three new structures of allosteric enzymes.