Disclosing the Structural Secrets of the HD-GYP Domains
HD-GYP proteins are the least studied and most mysterious class of cyclic di-GMP-dedicated phosphodiesterases. Rinaldo et al. (p. 1525–1535) report the structure of the HD-GYP domain of PA4781 from Pseudomonas aeruginosa. Compared to the other two solved structures of HD-GYP domains, PA4781 differs both in the binding mode and in the nature of the coordinated metal ions. This work enhances our general understanding of this fascinating family of phosphodiesterases, suggesting that these proteins are able to adapt their metal binding site to embrace different functions, thus disclosing an amazing multifunctional landscape.
Novel Features of the PhoPR-Mediated Phosphate Limitation Response in Bacillus subtilis
The PhoPR two-component system controls phosphate acquisition and cell wall anionic polymer metabolism (PHO response) in phosphate-limited Bacillus subtilis cells. Salzberg et al. (p. 1492–1506) identify 13 new phosphorylated PhoP (PhoP∼P) chromosomal binding sites that could not be predicted from previous transcriptome analyses. The role of PhoPR in cell wall metabolism is expanded by PhoP∼P binding to promoters that direct expression of minor teichoic acid and lipoteichoic acid synthetases. Interestingly, positive autoregulation of phoPR expression requires PhoP∼P to bind at the 3′ end of the operon. This indicates that the PHO response must be amplified by a novel mechanism in B. subtilis.
Elongated Escherichia coli Cells: to What Lengths Will E. coli Grow?
El-Hajj and Newman (p. 1507–1514) have isolated an Escherichia coli mutant that forms enormously long cells on subculture to low-osmolality medium, up to 700 times longer than the usual small rods that the mutant forms in high-osmolality medium. Upon incubation at low osmolality, the mutant rods elongate without visible subdivision and without loss of viability, segregating DNA over the entire length of continuous cytoplasm. The failure to divide may be related to their decreased levels of the essential division protein FtsZ. These very large cells make possible single-cell biochemical and physiological studies.
- Copyright © 2015, American Society for Microbiology. All Rights Reserved.
