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The molecular basis of redox sensitivity in proteins is not well understood. Here we consider a continuum of NO- and O2-related modifications of cysteine residues that constitute biological signaling events on the one hand and hallmarks of nitrosative and oxidative stresses on the other.
Formation of an internal (thio)ester bond activates numerous in vivo protein autoprocessing pathways including pyruvoyol group synthesis, autoproteolysis, protein splicing, enzyme activation and protein targeting. Structural analysis of precursors, intermediates and products is fine tuning our understanding of the mechanisms of these reactions.
How is it possible that nine small repeated ‘zinc finger’ units (each spanning just 3 or 4 base pairs) can protect the whole 50 base pair binding site of TFIIIA and why should such a periodic protein structure give rise to such an asymmetric footprint on DNA? The crystal structure of the first six fingers of TFIIIA bound to 31 base pairs of DNA explains everything: not all zinc fingers act alike.
The crystal structure of the heterodimeric transcriptional regulator GABPα/β bound to DNA reveals extensive protein–protein interactions between an ETS domain and ankyrin repeats that may influence DNA binding affinity.
The crystal structures of RCC1 and the Sec7 domain of human Arno, nucleotide exchange factors for the Ras-related GTPases Ran and ARF, reveal two very different folds, the former a seven-bladed β-propeller, the latter a capped right-handed superhelix. Both are also unrelated to the folds of Mss4 and elongation factor Ts, nucleotide exchange factors for Rab and elongation factor Tu.