Nucleoid-Associated Proteins HU and IHF: Oligomerization in Solution and Hydrodynamic Propertiesстатья
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Дата последнего поиска статьи во внешних источниках: 17 апреля 2024 г.
Аннотация:Structure and function of bacterial nucleoid is controlled by the nucleoid-associated proteins (NAP). In anyphase of growth, various NAPs, acting sequentially, condense nucleoid and facilitate formation of its transcriptionallyactive structure. However, in the late stationary phase, only one of the NAPs, Dps protein, is strongly expressed, andDNA–protein crystals are formed that transform nucleoid into a static, transcriptionally inactive structure, effectively protectedfrom the external influences. Discovery of crystal structures in living cells and association of this phenomenon withthe bacterial resistance to antibiotics has aroused great interest in studying this phenomenon. The aim of this work isto obtain and compare structures of two related NAPs (HU and IHF), since they are the ones that accumulate in the cellat the late stationary stage of growth, which precedes formation of the protective DNA–Dps crystalline complex. For structuralstudies, two complementary methods were used in the work: small-angle X-ray scattering (SAXS) as the main methodfor studying structure of proteins in solution, and dynamic light scattering as a complementary one. To interpret the SAXSdata, various approaches and computer programs were used (in particular, the evaluation of structural invariants, rigid bodymodeling and equilibrium mixture analysis in terms of the volume fractions of its components were applied), which made itpossible to determine macromolecular characteristics and obtain reliable 3D structural models of various oligomeric formsof HU and IHF proteins with ~2 nm resolution typical for SAXS. It was shown that these proteins oligomerize in solutionto varying degrees, and IHF is characterized by the presence of large oligomers consisting of initial dimers arranged ina chain. An analysis of the experimental and published data made it possible to hypothesize that just before the Dps expression,it is IHF that forms toroidal structures previously observed in vivo and prepares the platform for formation ofDNA–Dps crystals. The results obtained are necessary for further investigation of the phenomenon of biocrystal formationin bacterial cells and finding ways to overcome resistance of various pathogens to external conditions.