Cover image

Cover Two-component signal transduction guides adaptive behavior in all kingdoms of life. A pseudo-atomic model of the bacterial enhancer-binding protein NtrC, built by docking high-resolution structures into low-resolution density maps derived from small- and wide-angle X-ray scattering (SAXS/WAXS) and electron microscopy (EM) data, shows how the phosphorylated receiver domain (yellow) facilitates assembly of the ring form of this &agr;54-dependent AAA⁺ ATPase (red and white). Major conformational and order-disorder transitions of the GAFTGA-loops (white) and DNA-binding domains (blue) are demonstrated to accompany the nucleotide hydrolysis cycle; understanding the details of these will provide the mechanism by which these AAA⁺ ATPases perform mechanical work to remodel the &agr;54-polymerase-DNA complex. (For details, see De Carlo et al., p. 1485.)