RNAs actively cycle on the Sm-like protein Hfq.
Hfq, a protein required for small RNA (sRNA)-mediated regulation in bacteria, binds RNA with low-nanomolar K(d) values and long half-lives of complexes (>100 min). This cannot be reconciled with the 1- 2-min response time of regulation in vivo. We show that RNAs displace each other on Hfq on a short time scale by RNA concentration-driven (active) cycling. Already at submicromolar concentrations of competitor RNA, half-lives of RNA-Hfq complexes are ≈1 min. We propose that competitor RNA associates transiently with RNA-Hfq complexes, RNAs exchange binding sites, and one of the RNAs eventually dissociates. This solves the "strong binding-high turnover" paradox and permits efficient use of the Hfq pool.
Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Sweden.
Aurélie
A
Fender
Johan
J
Elf
Kornelia
K
Hampel
Bastian
B
Zimmermann
E Gerhart H
EG
Wagner
D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D035001:Host Factor 1 Protein / Q000378:metabolism*; D011485:Protein Binding; D012329:RNA, Bacterial / Q000378:metabolism*
D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D012329:RNA, Bacterial