| 1T6B |
Membrane Protein Toxin |
date |
May 05, 2004  |
|---|
| title | Crystal Structure Of B. Anthracis Protective Antigen Complexed With Human Anthrax Toxin Receptor |
| authors | E.Santelli, L.A.Bankston, S.H.Leppla, R.C.Liddington |
| compound |
source |
Molecule: Protective Antigen
Chain: X
Engineered: Yes
|
Organism_scientific: Bacillus Anthracis
Organism_common: Bacteria
Expression_system: Bacillus Anthracis
Expression_system_common: Bacteria
Expression_system_strain: Bh445
Expression_system_vector_type: Plasmid
|
Molecule: Anthrax Toxin Receptor 2
Chain: Y
Fragment: Ai Domain
Synonym: Capillary Morphogenesis Protein-2; Cmg-2
Engineered: Yes
|
Organism_scientific: Homo Sapiens
Organism_common: Human
Gene: Antxr2,Cmg2
Expression_system: Escherichia Coli
Expression_system_common: Bacteria
Expression_system_strain: Bl21(De3)
Expression_system_vector_type: Plasmid
Expression_system_plasmid: Pet15b
|
| symmetry | Space Group: P 21 21 21
| R_factor | 0.207 |
crystal
cell |
| length a |
length b |
length c |
angle alpha |
angle beta |
angle gamma |
| 88.160 |
94.118 |
135.597 |
90.00 |
90.00 |
90.00 |
|
| method | X-Ray Diffraction | resolution | 2.50 Å |
| ligand | CA, MN, NA, PG4
| enzyme |
|
| domain | Domain 4 appears to be a separate domain and shows limited contact with the other three domains: it would swing out of the way during membrane insertion. Binding to pa seems to be effected through the vwa domain. The subdomain 1b is part of the remaining 63-kda fragment (pa63) and contains the binding sites for lp and ef. Domain 2 is a beta-barrel core containing a large flexible loop that has been implicated in membrane insertion and pore formation. There is a chymotrypsin cleavage site in this loop that is required for toxicity. The molecule is folded into four functional domains. It is required for binding to the receptor; the small loop is involved in receptor recognition. Cleavage of the pa monomer releases the subdomain 1a, which is the n-terminal fragment of 20-kda (pa20). Domain 1 contains two calcium ions and the proteolytic activation site. Each domain is required for a particular step in the toxicity process. Domain 3 has a hydrophobic patch thought to be involved in protein-protein interactions. |
| similarity | Contains 1 vwfa domain. Belongs to the bacterial binary toxin family. Belongs to the atr family.[PA14] |
| subunit | Pa-63 forms heptamers and this oligomerization is required for lf or ef binding. Anthrax toxins are composed of three distinct proteins, a protective antigen (pa), a lethal factor (lf) and an edema factor (ef). This complex is endocytosed by the host. Binds laminin, and possibly also collagen type iv. Once activated, at low ph, the heptamer undergoes conformational changes and converts from prepore to pore inserted in the membrane, forming cation-selective channels and triggering the release of lf and ef in the host cytoplasm. None of these is toxic by itself. Pa+lf forms the lethal toxin (letx); pa+ef forms the edema toxin (edtx). Binds to the protective antigen (pa) of bacillus anthracis in a divalent cation-dependent manner, with the following preference: calcium > manganese > magnesium > zinc. Binding of pa leads to heptamerization of the receptor-pa complex. |
| post-translat. modifications | The release of pa20 from the remaining receptor-bound pa63 exposes the binding site for ef and lf, and promotes oligomerization and internalization of the protein. Proteolytic activation by furin or a furin-like protease cleaves the protein in two parts, pa-20 and pa-63; the latter is the mature protein. The cleavage occurs at the cell surface and probably in the serum of infected animals as well; both native and cleaved pa are able to bind to the cell receptor. |
| tissue | Expressed in prostate, thymus, ovary, testis, pancreas, colon, heart, kidney, lung, liver, peripheral blood leukocytes, placenta, skeletal muscle, small intestine and spleen. |
| subcellular loc. | Therefore, pa is translocated across the membrane in an unfolded state and then it is folded into its native configuration on the trans side of the membrane, prior to its release to the environment. Isoform 1 is expressed at the cell surface while isoform 2 is predominantly expressed within the endoplasmic reticulum and not at the plasma membrane. Secreted (isoform 3). Secreted through the sec-dependent secretion pathway. Type i membrane protein (isoforms 1 and 2). Pa requires the extracellular chaperone prsa for efficient folding. |
| genes | BXA0164, GBAA (B. anthracis); ANTXR2 (H. sapiens) |
| function | Pa associated with lf causes death when injected, pa associated with ef produces edema. One of the three proteins composing the anthrax toxin, the agent which infects many mammalian species and that may cause death. Pa induces immunity to infection with anthrax. Pa binds to a receptor (atr) in sensitive eukaryotic cells, thereby facilitating the translocation of the enzymatic toxin components, edema factor and lethal factor, across the target cell membrane. Necessary for cellular interactions with laminin and the extracellular matrix. |
Gene
Ontology | |
| disease | Fibromatosis,juvenile hyaline
Hyalinosis,infantilesystemic
Jhf is an autosomal recessive syndrome that is similar to ish but takes a milder course. This autosomal recessive syndrome is similar to jhf, but has an earlier onset and a more severe course. Patients develop multiple subcutaneous skin tumors and gingival hypertrophy. Symptoms appear at birth or within the first months of life, with painful, swollen joint contractures, osteopenia, osteoporosis and livid red hyperpigmentation over bony prominences. Defects in antxr2 are the cause of juvenile hyaline fibromatosis (jhf) [mim. 228600]. Hyaline deposits in multiple organs, recurrent infections and intractable diarrhea often lead to death within the first 2 years of life. Surviving children may suffer from severely reduced mobility due to joint contractures. Defects in antxr2 are the cause of infantile systemic hyalinosis (ish) [mim. 236490]. It is characterized by hyaline deposition in the dermis, multiple subcutaneous skin tumors and gingival hypertrophy, followed by progressive joint contractions, osteopenia and osteoporosis that may lead to a severe limitation of mobility. |
| Primary reference | Crystal structure of a complex between anthrax toxin and its host cell receptor., Santelli E, Bankston LA, Leppla SH, Liddington RC, Nature 2004 Aug 19;430(7002):905-8. Epub 2004 Jul 4. PMID:15243628 |
