2mw2
From Proteopedia
Hha-H-NS46 charge zipper complex
Structural highlights
Function[HHA_ECOLI] Down-regulates hemolysin production and can also stimulate transposition events in vivo. Binds DNA and influences DNA topology in response to environmental stimuli. Involved in persister cell formation, acting downstream of mRNA interferase (toxin) MqsR. Decreases biofilm formation by repressing the transcription of fimbrial genes fimA and ihfA, and by repressing the transcription of tRNAs corresponding to rare codons, which are abundant in type 1 fimbrial genes.[1] [2] [3] [4] [HNS_ECOLI] A DNA-binding protein implicated in transcriptional repression (silencing) as well as in bacterial chromosome organization. H-NS binds tightly to AT-rich dsDNA, increases its thermal stability and inhibits transcription. Also binds to ssDNA and RNA but with a much lower affinity. H-NS has possible histone-like function. May be a global transcriptional regulator through its ability to bind to curved DNA sequences, which are found in regions upstream of a certain subset of promoters. Plays a role in the thermal control of pili and adhesive curli fimbriae production, by inducing transcription of csgD. Represses the CRISPR-cas promoters, permits only weak transcription of the crRNA precursor; its role is antagonized by LeuO. Subject to transcriptional auto-repression. Binds preferentially to the upstream region of its own gene recognizing two segments of DNA on both sides of a bend centered around -150.[5] [6] [7] [8] Publication Abstract from PubMedThe Hha/YmoA nucleoid-associated proteins help selectively silence horizontally acquired genetic material, including pathogenicity and antibiotic resistance genes and their maintenance in the absence of selective pressure. Members of the Hha family contribute to gene silencing by binding to the N-terminal dimerization domain of H-NS and modifying its selectivity. Hha-like proteins and the H-NS N-terminal domain are unusually rich in charged residues, and their interaction is mostly electrostatic-driven but, nonetheless, highly selective. The NMR-based structural model of the complex between Hha/YmoA and the H-NS N-terminal dimerization domain reveals that the origin of the selectivity is the formation of a three-protein charge zipper with interdigitated complementary charged residues from Hha and the two units of the H-NS dimer. The free form of YmoA shows collective microsecond-millisecond dynamics that can by measured by NMR relaxation dispersion experiments and shows a linear dependence with the salt concentration. The number of residues sensing the collective dynamics and the population of the minor form increased in the presence of H-NS. Additionally, a single residue mutation in YmoA (D43N) abolished H-NS binding and the dynamics of the apo-form, suggesting the dynamics and binding are functionally related. A Three-protein Charge Zipper Stabilizes a Complex Modulating Bacterial Gene Silencing.,Cordeiro TN, Garcia J, Bernado P, Millet O, Pons M J Biol Chem. 2015 Aug 28;290(35):21200-12. doi: 10.1074/jbc.M114.630400. Epub, 2015 Jun 17. PMID:26085102[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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