Rapid binding and release of Hfq from ternary complexes during RNA annealing.

ABSTRACT: The Sm protein Hfq binds small non-coding RNA (sRNAs) in bacteria and facilitates their base pairing with mRNA targets. Molecular beacons and a 16 nt RNA derived from the Hfq binding site in DsrA sRNA were used to investigate how Hfq accelerates base pairing between complementary strands of RNA. Stopped-flow fluorescence experiments showed that annealing became faster with Hfq concentration but was impaired by mutations in RNA binding sites on either face of the Hfq ring or by competition with excess RNA substrate. A fast bimolecular Hfq binding step (∼10(8) M(-1)s(-1)) observed with Cy3-Hfq was followed by a slow transition (0.5 s(-1)) to a stable Hfq-RNA complex that exchanges RNA ligands more slowly. Release of Hfq upon addition of complementary RNA was faster than duplex formation, sug

SUBMITTER: Hopkins JF 

PROVIDER: S-EPMC3130257 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature