P.69 Pertactin Structure and Function: Difference between revisions
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==Introduction== | ==Introduction== | ||
Pertactin is a virulence toxin of ''Bordetella | '''Pertactin''' is a virulence toxin of ''Bordetella pertussis'' and close relatives, such as ''Bordetella parapertussis''. It is an outer surface membrane protein involved in the binding of ''B. pertussis'' to host cells, which aids the bacteria in infection of host cells with whooping cough. Many of the conserved regions in this protein, such as its passenger and autotransporter domains, contribute directly to the overall virulence and pathogenicity of these organisms. | ||
Autotransporters make up the largest protein family in Gram-negative bacteria. They are usually comprised of a C-terminal beta-barrel-shaped transporter domain anchored in the outer membrane and an N-terminal passenger domain that crosses the outer membrane through the beta barrel (Figure 1a). The autotransporter is considered a virulence factor with the passenger domain contributing to the virulence of the pathogen. This N-terminal domain is similar in structure between different species, but the functions vary greatly. However, the C-terminal beta-barrel domain is a highly conserved structure for transport across the membrane but can vary greatly in the sequence. Many factors including biogenesis, use of accessory proteins, and fate of the beta-barrel translocator are not well known. | Autotransporters make up the largest protein family in Gram-negative bacteria. They are usually comprised of a C-terminal beta-barrel-shaped transporter domain anchored in the outer membrane and an N-terminal passenger domain that crosses the outer membrane through the beta barrel (Figure 1a). The autotransporter is considered a virulence factor with the passenger domain contributing to the virulence of the pathogen. This N-terminal domain is similar in structure between different species, but the functions vary greatly. However, the C-terminal beta-barrel domain is a highly conserved structure for transport across the membrane but can vary greatly in the sequence. Many factors including biogenesis, use of accessory proteins, and fate of the beta-barrel translocator are not well known. | ||
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==3D image== | ==3D image== | ||
<Structure load='1dab' size='350' frame='true' align='left' caption='3D image of pertactin' scene='Insert optional scene name here' /> | <Structure load='1dab' size='350' frame='true' align='left' caption='3D image of pertactin (PDB code [[1dab]])' scene='Insert optional scene name here' /> | ||
==Structure and Protein Adhesion Properties== | ==Structure and Protein Adhesion Properties== | ||
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One of these features is the <scene name='71/716564/Arg_gly_asp/1'>Arg-Gly-Asp (RGD) tripeptide motif</scene> that allows for protein-protein interactions <ref name="EMS" />. This motif has been found in several proteins, and has been shown to support cell adhesion in most cases. A subset of cell-surface proteins, called integrins, act as receptors for cell adhesion molecules. These integrins recognize the RGD motif within their ligands, and allow for cell-substratum and cell-cell interactions <ref>D'Souza, S. E., Ginsberg, M. H., & Plow, E. F. (1991). Arginyl-glycyl-aspartic acid (RGD): a cell adhesion motif. Trends In Biochemical Sciences, 16(7), 246-250.</ref>. | One of these features is the <scene name='71/716564/Arg_gly_asp/1'>Arg-Gly-Asp (RGD) tripeptide motif</scene> that allows for protein-protein interactions <ref name="EMS" />. This motif has been found in several proteins, and has been shown to support cell adhesion in most cases. A subset of cell-surface proteins, called integrins, act as receptors for cell adhesion molecules. These integrins recognize the RGD motif within their ligands, and allow for cell-substratum and cell-cell interactions <ref>D'Souza, S. E., Ginsberg, M. H., & Plow, E. F. (1991). Arginyl-glycyl-aspartic acid (RGD): a cell adhesion motif. Trends In Biochemical Sciences, 16(7), 246-250.</ref>. | ||
Additionally, P.69 contains two <scene name='71/716564/Proline/3'>proline-rich regions</scene> which are thought to provide important binding sites, and are characteristic of proteins exhibiting binding capabilities <ref name="EMS" />. Proline is a very unusual amino acid, and its structure limits the possible conformations it can adopt. The rigidity of these structures allow for reliable binding sites in many different proteins especially when chains of proline are bound to each other. These regions are typically non-specific, and allow for rapid binding. This is advantageous due to the wide range of ligands that can be bound, increasing the versatility of the proteins that utilize these regions <ref>Williamson, M. P. (1994). The structure and function of proline-rich regions in proteins. Biochemical Journal, 297(Pt 2), 249–260.</ref>. | Additionally, P.69 contains two <scene name='71/716564/Proline/3'>proline-rich regions</scene> which are thought to provide important binding sites, and are characteristic of proteins exhibiting binding capabilities <ref name="EMS" />. Proline is a very unusual amino acid, and its structure limits the possible conformations that it can adopt. The rigidity of these structures allow for reliable binding sites in many different proteins especially when chains of proline are bound to each other. These regions are typically non-specific, and allow for rapid binding. This is advantageous due to the wide range of ligands that can be bound, increasing the versatility of the proteins that utilize these regions <ref>Williamson, M. P. (1994). The structure and function of proline-rich regions in proteins. Biochemical Journal, 297(Pt 2), 249–260.</ref>. | ||
The linear form of pertactin that protrudes from the surface of ''B. pertussis'' also has a high surface area that could be well suited for targeting mammalian cells <ref name="EMS" />. Studies have shown that adhesive area strongly affects integrin binding and adhesion strength. The positioning of binding regions also affects adhesion strength, making the combination of these two factors particularly important for proteins that serve this function <ref>Gallant, N. D., Michael, K. E., & García, A. J. (2005). Cell Adhesion Strengthening: Contributions of Adhesive Area, Integrin Binding, and Focal Adhesion Assembly. Molecular Biology of the Cell, 16(9), 4329–4340.</ref>. | The linear form of pertactin that protrudes from the surface of ''B. pertussis'' also has a high surface area that could be well suited for targeting mammalian cells <ref name="EMS" />. Studies have shown that adhesive area strongly affects integrin binding and adhesion strength. The positioning of binding regions also affects adhesion strength, making the combination of these two factors particularly important for proteins that serve this function <ref>Gallant, N. D., Michael, K. E., & García, A. J. (2005). Cell Adhesion Strengthening: Contributions of Adhesive Area, Integrin Binding, and Focal Adhesion Assembly. Molecular Biology of the Cell, 16(9), 4329–4340.</ref>. | ||
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==Pertactin vs Pertussis Toxin: Virulence Factors== | ==Pertactin vs Pertussis Toxin: Virulence Factors== | ||
Pertactin and Pertussis toxin (See Below) are both virulence factors that contribute to respiratory tract infection and whooping cough. Both are responsible for binding the foreign bacterial cell to the host organism’s cells. Despite similar functions, Pertactin and Pertussis toxin have very different structures. Pertussis toxin is a virulence factor only produced by ''Bordetella pertussis''. It is known to cause systemic symptoms of pertussis disease, such as leukocytosis and histamine sensitivity. It has also, recently, been discovered to promote respiratory infection by inhibiting and modulating host cell immune responses. Pertussis toxin promotes infection by acting as a soluble factor, which attacks resident cells of the trachea and lungs, such as macrophages<ref name= "Car">Carbonetti, Nicholas H. “Pertussis Toxin and Adenylate Cyclase Toxin: Key Virulence Factors of Bordetella Pertussis and Cell Biology Tools.” Future microbiology 5 (2010): 455–469. PMC. Web. 17 Nov. 2015.</ref>. Pertactin is also a virulence factor known to contribute to whooping cough. Pertactin is found in ''Bordetella pampertussis'', and a 91.3% homologous protein is found in ''Bordetella pertussis'', the species which produces Pertussis toxin. An amino acid alignment between the two strains reveals that the proteins differ in the number of repeated sequences. ''B. pampertussis'' has a series of approximately twenty more amino acids beginning at the 580th position ([[Media:Prn6.png| Figure 6]]). Similarly to Pertussis toxin, Pertactin is involved in binding the bacterial cell to respiratory host cells, however, less is known about the specific cells Pertactin binds to in order to promote infection.<ref name="CON" /> | |||
Despite similar functions, Pertussis toxin and Pertactin have very different structures. As mentioned previously, Pertactin’s structure consists of a 16-stranded parallel beta-helix with a v-shaped cross section, while Pertussis toxin consists of five subunits.<ref name="CON" />BLAST results of Pertactin revealed that two domains, autotransporter and PL1_Passenger_AT, are conserved. The autotransporter domain is located at the C-terminus of Pertactin and functions to transport the passenger domain, located at the N-terminus of Pertactin, in to the host cell, where the two domains are typically cleaved.<ref name="CON" /> This process is responsible for the bacterial cell binding to the host cell. While Pertactin is a single polypeptide chain, Pertussis toxin consists of five different subunits: S1 makes up subunit A and subunit B is a pentameric ring made of S2, S3, two S4 and S5. BLAST results revealed that a single domain is contained within subunits 1, 4 and 5: Pertussis_S1 superfamily, Pertussis_S4 superfamily and Pertussis_S5 superfamily. Subunits 2 and 3 contain an ATP superfamily and Pertussis_S2S3 Superfamily, which represent the N-terminal domain of aerolysin and pertussis toxin and the C-terminal domain, respectively. The individual structures may be responsible for Pertussis toxin’s ability to recognize receptors on numerous cell types<ref name="Car" />. | |||
As a whole, Pertactin and Pertussis toxin are structurally very different. However, amino acid alignments between Pertactin and each of the five subunits of Pertussis toxin reveals that various sections of Pertactin are the same or highly similar to individual subunits of Pertussis toxin ([[Media:Prn1.png | Figure 1]], [[Media:Prn2.png | Figure 2]], [[Media:Prn3.png | Figure 3]], [[Media:Prn4.png | Figure 4]], [[Media:Prn5.png | Figure 5]]). BLAST results also revealed that subunits 4 and 5’s structures consist of an OB fold and a closed or partly open beta barrel.<ref name="CON" /> Similar amino acid sequences, as well as similarities between Pertactin’s beta barrel structure and the beta barrel structures of subunits 4 and 5 may be how Pertactin and Pertussis toxin have similar functions. | |||
[[Image:Prn1.png]] | [[Image:Prn1.png]] | ||
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[[Image:Prn6.png]] | [[Image:Prn6.png]] | ||
==Pertussis Toxin== | |||
{{:Pertussis_Toxin-ATP_Complex}} | {{:Pertussis_Toxin-ATP_Complex}} | ||
Supplemental Information | ==Supplemental Information== | ||
#REDIRECT [[1dab]] | #REDIRECT [[1dab]] | ||
== References == | == References == | ||
<references/> | <references/> | ||