6tob | pdb_00006tob
Structural and DNA Binding Properties of Mycobacterial Integration Host Factor mIHF
Structural highlights
FunctionIHF_MYCTU A nucleoid-associated protein (NAP) required for septum formation and normal cell division as well as for DNA segregation. Binds about 135 sites across the chromosome, most of which are genes involved in virulence; most DNA-binding sites are immediately upstream of transcription start sites. When mIHF is depleted most of the genes are down-regulated (PubMed:30242166). Binds supercoiled and linear dsDNA in a concentration-dependent manner, probably non-sequence specifically. Binding compacts DNA, protecting it from degradation. Initial binding to supercoiled DNA opens it fully, followed by bending and compaction. Bends and thus compacts linear DNA (PubMed:23922883). Binds DNA via 2 sites, forms left-handed loops on linear DNA; at low concentrations unwinds larger cosmids (42.6 kb) then collapses and condenses DNA as protein levels rise. Forms mostly left-handed loops on condensing cosmid DNA (PubMed:31846718).[1] [2] [3] Publication Abstract from PubMedIn bacteria, nucleoid associated proteins (NAPs) take part in active chromosome organization by supercoil management, three-dimensional DNA looping and direct transcriptional control. Mycobacterial integration host factor (mIHF, rv1388) is a NAP restricted to Actinobacteria and essential for survival of the human pathogen Mycobacterium tuberculosis. We show in vitro that DNA binding by mIHF strongly stabilizes the protein and increases its melting temperature. The structure obtained by Nuclear Magnetic Resonance (NMR) spectroscopy characterizes mIHF as a globular protein with a protruding alpha helix and a disordered N-terminus, similar to Streptomyces coelicolor IHF (sIHF). NMR revealed no residues of high flexibility, suggesting that mIHF is a rigid protein overall that does not undergo structural rearrangements. We show that mIHF only binds to double stranded DNA in solution, through two DNA binding sites (DBSs) similar to those identified in the x-ray structure of sIHF. According to Atomic Force Microscopy, mIHF is able to introduce left-handed loops of ca. 100 nm size ( approximately 300 bp) in supercoiled cosmids, thereby unwinding and relaxing the DNA. Structural and DNA Binding Properties of Mycobacterial Integration Host Factor mIHF.,Odermatt NT, Lelli M, Herrmann T, Abriata LA, Japaridze A, Voilquin H, Singh R, Piton J, Emsley L, Dietler G, Cole ST J Struct Biol. 2019 Dec 14:107434. doi: 10.1016/j.jsb.2019.107434. PMID:31846718[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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