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Later this year, two issues of Nature Structural Biology will focus on specific topics: how RNA– protein machines work, and methods for monitoring conformational changes in biomolecules.
Phosphoribosylanthranilate isomerase (PRAI) and indole-3-glycerol phosphate synthase (IGPS) are distantly related α/β-barrel enzymes that catalyze successive steps in tryptophan biosynthesis. A ‘new’ PRAI was evolved from an ‘old’ IGPS by random mutagenesis followed by DNA shuffling and in vivo selection.
Structures of several structurally and functionally divergent MHC class I homologs and receptor complexes have recently been determined. They reveal the unusual versatility of the underlying MHC class I fold.
Apurinic/apyrmidinic endonuclease 1 (APE1) plays a central role in DNA repair by cleaving the DNA backbone 5′ of AP sites that result from removal of damaged bases. New structural findings on APE1–DNA cocrystals provide insights into how this enzyme binds and cleaves its substrate and how, like one member in an efficient relay team, it coordinates potentially dangerous steps in the base excision repair pathway.
The crystal structure of the universal ribonucleoprotein core of the signal recognition particle suggests that the RNA moiety has been evolutionarily conserved because it plays an important role in signal sequence recognition.
The structure of the trifunctional clavaminic acid synthase exhibits an emerging structural motif found among nonheme iron oxygen activating enzymes that provides the metal active site the flexibility to catalyze a remarkable range of reactions.
High resolution structures of the Tet and Lac repressors bound to their respective operator DNA sites provide endpoints for the functional allosteric pathways in these distinct regulatory systems.
