Ferritins: furnishing proteins with iron

Ferritins are a superfamily of iron oxidation, storage and mineralization proteins found throughout the animal, plant, and microbial kingdoms. The majority of ferritins consist of 24 subunits that individually fold into 4-α-helix bundles and assemble in a highly symmetric manner to form an approximately spherical protein coat around a central cavity into which an iron-containing mineral can be formed. Channels through the coat at inter-subunit contact points facilitate passage of iron ions to and from the central cavity, and intrasubunit catalytic sites, called ferroxidase centers, drive Fe2+ oxidation and O2 reduction. Though the different members of the superfamily share a common structure, there is often little amino acid sequence identity between them. Even where there is a high degree of sequence identity between two ferritins there can be major differences in how the proteins handle iron. In this review we describe some of the important structural features of ferritins and their mineralized iron cores and examine in detail how three selected ferritins oxidise Fe2+ in order to explore the mechanistic variations that exist amongst ferritins. We suggest that the mechanistic differences reflect differing evolutionary pressures on amino acid sequences, and that these differing pressures are a consequence of different primary functions for different ferritins

In situ localization by double-labeling immunoelectron microscopy of anti-neutrophil cytoplasmic autoantibodies in neutrophils and monocytes

Abstract Anti-neutrophil cytoplasmic autoantibodies (ANCA) associated with active Wegener's granulomatosis are directed against a soluble 29-Kd protein present in human neutrophils and monocytes. Affinity labeling with tritiated diisopropylfluorophosphate (3H-DFP) suggested that ANCA- antigen is a serine protease. We used immunoelectron microscopy to study the in situ localization of the ANCA-antigen in normal human neutrophils and monocytes using immunoglobulin G (IgG) from ANCA- positive patients and a mouse monoclonal antibody against the ANCA- antigen. Label was observed on the large granules of the neutrophils and in granules of monocytes. Double-labeling, using anti- myeloperoxidase or the peroxidase reaction as markers for azurophil granules and anti-lactoferrin as marker for specific granules, showed that ANCA is colocalized with markers of azurophil granules but not with lactoferrin. Furthermore, elastase and cathepsin G were found in the azurophil granules of neutrophils and in the peroxidase-positive granules of monocytes, colocalized with ANCA-antigen. Cytochalasin-B- treated neutrophils stimulated with N-formyl-methionyl-leucyl- phenylalanine (fMLP) formed large intracellular vacuoles and were partially degranulated. Some vacuoles contained ANCA-antigen, as well as myeloperoxidase, elastase, and cathepsin G, demonstrating release of these enzymes from the azurophil granules into vacuoles. Our results demonstrate that ANCA-antigen is located in myeloperoxidase-containing granules of neutrophils and monocytes, and is packaged in the same granules as elastase and cathepsin G, the two previously identified serine proteases of myeloid leukocytes.</jats:p

In situ localization by double-labeling immunoelectron microscopy of anti-neutrophil cytoplasmic autoantibodies in neutrophils and monocytes

Anti-neutrophil cytoplasmic autoantibodies (ANCA) associated with active Wegener's granulomatosis are directed against a soluble 29-Kd protein present in human neutrophils and monocytes. Affinity labeling with tritiated diisopropylfluorophosphate (3H-DFP) suggested that ANCA- antigen is a serine protease. We used immunoelectron microscopy to study the in situ localization of the ANCA-antigen in normal human neutrophils and monocytes using immunoglobulin G (IgG) from ANCA- positive patients and a mouse monoclonal antibody against the ANCA- antigen. Label was observed on the large granules of the neutrophils and in granules of monocytes. Double-labeling, using anti- myeloperoxidase or the peroxidase reaction as markers for azurophil granules and anti-lactoferrin as marker for specific granules, showed that ANCA is colocalized with markers of azurophil granules but not with lactoferrin. Furthermore, elastase and cathepsin G were found in the azurophil granules of neutrophils and in the peroxidase-positive granules of monocytes, colocalized with ANCA-antigen. Cytochalasin-B- treated neutrophils stimulated with N-formyl-methionyl-leucyl- phenylalanine (fMLP) formed large intracellular vacuoles and were partially degranulated. Some vacuoles contained ANCA-antigen, as well as myeloperoxidase, elastase, and cathepsin G, demonstrating release of these enzymes from the azurophil granules into vacuoles. Our results demonstrate that ANCA-antigen is located in myeloperoxidase-containing granules of neutrophils and monocytes, and is packaged in the same granules as elastase and cathepsin G, the two previously identified serine proteases of myeloid leukocytes.</jats:p

The External Dimension of EU Justice and Home Affairs: Tools, Processes, Outcomes

This working document offers a conceptual framework for understanding the processes underpinning the external dimension of EU Justice and Home Affairs (ED-JHA). Practically, it defines how the export of JHA principles and norms inform the geopolitical ambitions of the EU, i.e. the use of space for political purposes, or the control and management of people, objects and movement. The author begins by investigating how the ENP reconfigures the ED-JHA, and then goes on to discuss various conceptual stances on governance, specifically institutionalism, constructivism, and policy instruments. To conclude he traces the evolution of this external dimension, emphasising, whenever possible, its continuities and bifurcations. Overall, the aim is to ascertain the extent to which conceptual designs clarify or advance our knowledge of the contents and rationales of the ED-JHA