ABSTRACT
The serpin superfamily of protease inhibitors undergoes a remarkable conformational change to inhibit target proteases. To date, over 80 different serpin crystal structures have been determined. These data reveal that the serpin monomer can adopt five different conformations (native, partially inserted native, δ-form, latent, and cleaved). Further, recent studies have also revealed that serpins can domain swap; biochemical data suggest such an event underlies serpin polymerization in diseases such as antitrypsin deficiency. Here, we provide a comprehensive analysis on crystallization of serpins in context of the structural landscape of the serpin superfamily.
Subject(s)
Antithrombin III/isolation & purification , Crystallization/methods , Crystallography, X-Ray/methods , Molecular Biology/methods , Plasminogen Activator Inhibitor 1/isolation & purification , Recombinant Fusion Proteins/isolation & purification , alpha 1-Antitrypsin/isolation & purification , Animals , Antithrombin III/biosynthesis , Antithrombin III/genetics , CHO Cells , Chickens , Cricetinae , Escherichia coli , HEK293 Cells , Humans , Mice , Models, Molecular , Plasminogen Activator Inhibitor 1/biosynthesis , Plasminogen Activator Inhibitor 1/genetics , Polymerization , Protein Folding , Protein Structure, Secondary , Recombinant Fusion Proteins/biosynthesis , Recombinant Fusion Proteins/genetics , alpha 1-Antitrypsin/biosynthesis , alpha 1-Antitrypsin/geneticsABSTRACT
The membrane-attack complex (MAC) of complement pathway and perforin (PF) are important tools deployed by the immune system to target pathogens. Both perforin and the C9 component of the MAC contain a common 'MACPF' domain and form pores in the cell membrane as part of their function. The MAC targets gram-negative bacteria and certain pathogenic parasites, while perforin, released by natural killer cells or cytotoxic T lymphocytes (CTLs), targets virus-infected and transformed host cells (1). Remarkably, recent structural studies show that the MACPF domain is homologous to the pore-forming portion of bacterial cholesterol-dependent cytolysins; these data have provided important insight into the mechanism of pore-forming MACPF proteins. In addition to their role in immunity, MACPF family members have been identified as animal venoms, factors required for pathogen migration across host cell membranes and factors that govern developmental processes such as embryonic patterning and neuronal guidance (2). While most MACPF proteins characterized to date either form pores or span lipid membranes, some do not (e.g. the C6 component of the MAC). A current challenge is thus to understand the role, pore forming or otherwise, of MACPF proteins in developmental biology. This review discusses structural and functional diversity of the mammalian MACPF proteins.
Subject(s)
Complement Membrane Attack Complex/chemistry , Complement Membrane Attack Complex/immunology , Perforin/chemistry , Perforin/immunology , Animals , Cell Cycle Proteins , Complement Membrane Attack Complex/genetics , GTP Phosphohydrolases/chemistry , GTP Phosphohydrolases/genetics , GTP Phosphohydrolases/immunology , Glycoproteins/chemistry , Glycoproteins/genetics , Glycoproteins/immunology , Humans , Immunity, Cellular , Immunity, Humoral , Membrane Proteins/chemistry , Membrane Proteins/genetics , Membrane Proteins/immunology , Mice , Models, Molecular , Nerve Tissue Proteins/chemistry , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/immunology , Nuclear Proteins/chemistry , Nuclear Proteins/genetics , Nuclear Proteins/immunology , Perforin/genetics , Pore Forming Cytotoxic Proteins , Protein Multimerization , Protein Structure, TertiaryABSTRACT
Alpha1-antitrypsin deficiency, which can lead to both emphysema and liver disease, is a result of the accumulation of alpha1-antitrypsin polymers within the hepatocyte. A wealth of biochemical and biophysical data suggests that alpha1-antitrypsin polymers form via insertion of residues from the reactive center loop of one molecule into the beta-sheet of another. However, this long-standing hypothesis has not been confirmed by direct structural evidence. Here, we describe the first crystallographic evidence of a beta-strand linked polymer form of alpha1-antitrypsin: the crystal structure of a cleaved alpha1-antitrypsin polymer.
