title: Iron translocation into and out of Listeria innocua Dps and size distribution of the protein-enclosed nanomineral are modulated by the electrostatic gradient at the 3-fold "ferritin-like" pores.
abstract: Elucidating pore function at the 3-fold channels of 12-subunit, microbial Dps proteins is important in understanding their role in the management of iron/hydrogen peroxide. The Dps pores are called "ferritin-like" because of the structural resemblance to the 3-fold channels of 24-subunit ferritins used for iron entry and exit to and from the protein cage. In ferritins, negatively charged residues lining the pores generate a negative electrostatic gradient that guides iron ions toward the ferroxidase centers for catalysis with oxidant and destined for the mineralization cavity. To establish whether the set of three aspartate residues that line the pores in Listeria innocua Dps act in a similar fashion, D121N, D126N, D130N, and D121N/D126N/D130N proteins were produced; kinetics of iron uptake/release and the size distribution of the iron mineral in the protein cavity were compared. The results, discussed in the framework of crystal growth in a confined space, indicate that iron uses the hydrophilic 3-fold pores to traverse the protein shell. For the first time, the strength of the electrostatic potential is observed to modulate kinetic cooperativity in the iron uptake/release processes and accordingly the size distribution of the microcrystalline iron minerals in the Dps protein population.
authors.affiliation: CNR Institute of Molecular Biology and Pathology, Department of Biochemical Sciences, University of Rome, 00185 Rome, Italy.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Bellapadrona
authors.forename: Simonetta
authors.initials: S
authors.lastname: Stefanini
authors.forename: Carlotta
authors.initials: C
authors.lastname: Zamparelli
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Theil
authors.forename: Emilia
authors.initials: E
authors.lastname: Chiancone
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D002384:Catalysis; D003460:Crystallization; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D005293:Ferritins / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D008087:Listeria / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D016877:Oxidants / Q000737:chemistry; D011506:Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C083911:DPS protein, Bacteria; D016877:Oxidants; D011506:Proteins; D005293:Ferritins; D007501:Iron