title: The structures of mutant forms of Hfq from Pseudomonas aeruginosa reveal the importance of the conserved His57 for the protein hexamer organization.
abstract: The bacterial Sm-like protein Hfq forms homohexamers both in solution and in crystals. The monomers are organized as a continuous beta-sheet passing through the whole hexamer ring with a common hydrophobic core. Analysis of the Pseudomonas aeruginosa Hfq (PaeHfq) hexamer structure suggested that solvent-inaccessible intermonomer hydrogen bonds created by conserved amino-acid residues should also stabilize the quaternary structure of the protein. In this work, one such conserved residue, His57, in PaeHfq was replaced by alanine, threonine or asparagine. The crystal structures of His57Thr and His57Ala Hfq were determined and the stabilities of all of the mutant forms and of the wild-type protein were measured. The results obtained demonstrate the great importance of solvent-inaccessible conserved hydrogen bonds between the Hfq monomers in stabilization of the hexamer structure.
authors.affiliation: Institute of Protein Research, RAS, Russia.
authors.forename: Olga
authors.initials: O
authors.lastname: Moskaleva
authors.forename: Bogdan
authors.initials: B
authors.lastname: Melnik
authors.forename: Azat
authors.initials: A
authors.lastname: Gabdulkhakov
authors.forename: Maria
authors.initials: M
authors.lastname: Garber
authors.forename: Stanislav
authors.initials: S
authors.lastname: Nikonov
authors.forename: Elena
authors.initials: E
authors.lastname: Stolboushkina
authors.forename: Alexei
authors.initials: A
authors.lastname: Nikulin
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D006639:Histidine / Q000235:genetics; D035001:Host Factor 1 Protein / Q000737:chemistry* / Q000235:genetics; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000737:chemistry* / Q000235:genetics
chemical_list: D035001:Host Factor 1 Protein; D006639:Histidine