Structure and Inter-domain Interactions of Domain II from the Blood-stage Malarial Protein, Apical Membrane Antigen 1

Feng, Zhiping; Keizer, David W; Stevenson, R.; Yao, Shenggen; Babon, Jeffrey J.; Murphy, Vincent J.; Anders, Robin F.; Norton, Raymond S.

doi:10.1016/j.jmb.2005.05.011

Cited by 31 publications

(19 citation statements)

References 68 publications

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“…Most AMA1 epitopes recognized by antibodies in human sera are discontinuous (56,57), and the formation of correct disulfide bonds in the protein is required for the induction of significant levels of inhibitory antibody following immunization (1). The solution structure of E. coli-expressed and refolded DII and DIII has been determined by nuclear magnetic resonance methods (14,42). Both domains are substantially more disordered than the corresponding regions in the structure of the entire ectodomain established by X-ray Even without optimization of fermentation and purification, the AMm and MmA fusion proteins were produced in good yield and with a main band purity of over 95% as judged by SDS-PAGE.…”

Section: Discussionmentioning

confidence: 99%

Malaria Vaccine-Related Benefits of a Single Protein ComprisingPlasmodium falciparumApical Membrane Antigen 1 Domains I and II Fused to a Modified Form of the 19-Kilodalton C-Terminal Fragment of Merozoite Surface Protein 1

Faber

Remarque

Morgan³

et al. 2007

Infect Immun

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We show that the smallest module of Plasmodium falciparum AMA1 (PfAMA1) that can be expressed in the yeast Pichia pastoris while retaining the capacity to induce high levels of parasite-inhibitory antibodies comprises domains I and II. Based on this, two fusion proteins, differing in the order of the modules, were The annual malaria burden of 300 to 500 million clinical cases results in an estimated mortality for up to 2 million people, predominantly sub-Saharan African children under 5 years of age (52). A malaria vaccine would make a significant contribution to reducing the enormous socioeconomic burden caused by this disease. A number of vaccine approaches, targeting various stages of the complex parasite life cycle, are being investigated (21). Apical membrane antigen 1 (AMA1) and merozoite surface protein 1 (MSP1) are potential vaccine components, and a number of vaccines using elements of these molecules are currently in early clinical evaluation. Previous research has indicated that a combination of MSP1 and AMA1 has vaccine-related advantages over either antigen alone (3, 55). Both molecules are essential components of the asexual blood-stage merozoite (50, 60), the developmental stage of the parasite stage responsible for invasion of erythrocytes. They are also both present on merozoites that emerge from infected liver cells, and AMA1 has also been identified as a sporozoite protein (51). Plasmodium falciparum AMA1 (PfAMA1) is a polymorphic protein; over 10% of its amino acid residues can change without obvious effects on its function in invasion. With few exceptions, polymorphic residues are bi-or trimorphic, and all are located on the outside of the molecule, predominantly on one face (47). One strategy to tackle any potential negative effect of polymorphism in vaccine development is to combine PfAMA1 with other targets that are not, or are less, polymorphic, such as MSP1 19 (59). A single-protein vaccine has cost, speed, and potential functionality benefits compared with vaccines prepared from mixtures of proteins. We have therefore investigated how minimal elements of AMA1 and MSP1, each retaining the ability to induce growth-inhibitory antibodies, can be incorporated into fusion proteins that allow the development of single-protein, multitarget malaria vaccines.Micronemes are organelles of the merozoite apical complex, a structure intimately associated with the invasion of erythrocytes. AMA1 is initially trafficked to micronemes as an 83-kDa type 1 integral membrane protein; subsequently, the N-terminal prodomain is proteolytically cleaved prior to relocalization to the merozoite outer membrane (43). Further cleavage, proximal to the transmembrane region, then releases the ectodomain from the parasite surface (26). AMA1 contains 16 conserved cysteine residues that form eight intramolecular disulfide bonds (20). The recently elucidated three-dimensional structure of AMA1 (47) confirms that after cleavage of the prodomain, the ectodomain essentially comprises three interacting domains (DI, DII, and D...

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Section: Discussionmentioning

confidence: 99%

Malaria Vaccine-Related Benefits of a Single Protein ComprisingPlasmodium falciparumApical Membrane Antigen 1 Domains I and II Fused to a Modified Form of the 19-Kilodalton C-Terminal Fragment of Merozoite Surface Protein 1

Faber

Remarque

Morgan³

et al. 2007

Infect Immun

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“…28 In addition, NMR solution structures have been determined for the individual domains II and III. 21,29 These results provide a structural basis for analysing polymorphism and protecting B-cell epitopes in AMA1, factors that can be key to understanding the function of the protein and to its eventual optimisation as a vaccine candidate. Polymorphism, which has been studied extensively in the P. falciparum homologue, PfAMA1, is under strong diversifying selection pressure from the immune response of the host.…”

Section: Introductionmentioning

confidence: 97%

Cross-reactivity Studies of an Anti-Plasmodium vivax Apical Membrane Antigen 1 Monoclonal Antibody: Binding and Structural Characterisation

Igonet

Normand

Faure

et al. 2007

Journal of Molecular Biology

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“…8D. Moreover, although P. falciparum AMA1 residues 380 to 385 (LPTGAF) are not visible in the crystal structure of the ectodomain of P. vivax AMA1 because they are present on a flexible loop of domain II whose structure could not be resolved (15,38), the closest discernible residues are indeed juxtaposed to the RLPcontaining sequence in the P. vivax structure. These data support the view that the J1 peptide is acting as a scaffold to hold two regions in the appropriate spatial orientation for efficient binding of 4G2dc1.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, 4G2dc1 reacted with AMA1 in 10 different isolates of P. falciparum from diverse geographical locations and consistently inhibited the invasion of P. falciparum merozoites into erythrocytes by 60 to 70% in vitro (25). The exact location of the 4G2dc1 conformational epitope is not known, but it appears to include a number of residues from a loop in domain II of AMA1 (38), which shows some conformational flexibility (15,38). Nonetheless, it is clearly important for the generation of protective antibodies that can block merozoite invasion.…”

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confidence: 99%

Mimotopes of Apical Membrane Antigen 1: Structures of Phage-Derived Peptides Recognized by the Inhibitory Monoclonal Antibody 4G2dc1 and Design of a More Active Analogue

et al. 2007

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Apical membrane antigen 1 (AMA1) of the malaria parasite Plasmodium falciparum is an integral membrane protein that plays a key role in merozoite invasion of host erythrocytes. A monoclonal antibody, 4G2dc1, recognizes correctly folded AMA1 and blocks merozoite invasion. Phage display was used to identify peptides that bind to 4G2dc1 and mimic an important epitope of AMA1. Three of the highest-affinity binders-J1, J3, and J7-were chosen for antigenicity and immunogenicity studies. J1 and J7 were found to be true antigen mimics since both peptides generated inhibitory antibodies in rabbits (J. L. Casey et al., Infect. Immun. 72:1126-1134, 2004). In the present study, the solution structures of all three mimotopes were investigated by nuclear magnetic resonance spectroscopy. J1 adopted a well-defined region of structure, which can be attributed in part to the interactions of Trp11 with surrounding residues. In contrast, J3 and J7 did not adopt an ordered conformation over the majority of residues, although they share a region of local structure across their consensus sequence. Since J1 was the most structured of the peptides, it provided a template for the design of a constrained analogue, J1cc, which shares a structure similar to that of J1 and has a disulfide-stabilized conformation around the Trp11 region. J1cc binds with greater affinity to 4G2dc1 than does J1. These peptide structures provide the foundation for a better understanding of the complex conformational nature of inhibitory epitopes on AMA1. With its greater conformational stability and higher affinity for AMA1, J1cc may be a better in vitro correlate of immunity than the peptides identified by phage display.Malaria infects 300 to 500 million people per year worldwide and causes 2 to 3 million deaths, mainly in children under 5 years of age. A considerable effort is being devoted to the development of a vaccine against malaria, and one of the leading candidates for inclusion in such a vaccine is apical membrane antigen 1 (AMA1), a type I integral membrane protein conserved throughout all Plasmodium species. AMA1 is critical for the invasion of host erythrocytes (36) and is translocated from the micronemes onto the parasite surface around the time of invasion (20). Although its precise role in invasion remains undefined, it has been postulated that AMA1 is involved in realignment of the parasite after attachment to the erythrocyte, ensuring that the apical prominence of the merozoite is in close proximity to the erythrocyte surface (8, 33). Recombinant AMA1 induced protective immune responses in mouse and monkey models of malaria (2, 10, 11, 13), and both monoclonal and polyclonal antibodies to AMA1 inhibit merozoite invasion of erythrocytes (2,9,11,12,25,34,42). The observation that it was not possible to obtain targeted gene disruptions of the AMA1 gene that knocked out the function of the protein further supports an important role for AMA1 in the invasion of host erythrocytes (43). Recently, a conditional knockout of Toxoplasma gondii AMA1 was cre...

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Structure and Inter-domain Interactions of Domain II from the Blood-stage Malarial Protein, Apical Membrane Antigen 1

Cited by 31 publications

References 68 publications

Malaria Vaccine-Related Benefits of a Single Protein ComprisingPlasmodium falciparumApical Membrane Antigen 1 Domains I and II Fused to a Modified Form of the 19-Kilodalton C-Terminal Fragment of Merozoite Surface Protein 1

Malaria Vaccine-Related Benefits of a Single Protein ComprisingPlasmodium falciparumApical Membrane Antigen 1 Domains I and II Fused to a Modified Form of the 19-Kilodalton C-Terminal Fragment of Merozoite Surface Protein 1

Cross-reactivity Studies of an Anti-Plasmodium vivax Apical Membrane Antigen 1 Monoclonal Antibody: Binding and Structural Characterisation

Mimotopes of Apical Membrane Antigen 1: Structures of Phage-Derived Peptides Recognized by the Inhibitory Monoclonal Antibody 4G2dc1 and Design of a More Active Analogue

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