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Das S, Manna A, Majumdar O, Dhara L. M- O-M mediated denaturation resistant P2 tetramer on the infected erythrocyte surface of malaria parasite imports serum fatty acids. iScience 2024; 27:109760. [PMID: 38726364 PMCID: PMC11079477 DOI: 10.1016/j.isci.2024.109760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 04/01/2024] [Accepted: 04/15/2024] [Indexed: 05/12/2024] Open
Abstract
In Plasmodium falciparum, DNA replication, and asynchronous nuclear divisions precede cytokinesis during intraerythrocytic schizogony. Regulation of nuclear division through the import of serum components was largely unknown. At the trophozoite stage, P. falciparum ribosomal protein P2 (PfP2) is exported to the infected erythrocyte (IE) cytosol and the surface as a denaturation-resistant tetramer. The inaccessibility of the IE surface exposed PfP2 to its bona fide ligand led to the arrest of nuclear division. Here, we show that at the onset of schizogony, denaturation-resistant PfP2 tetramer on the IE surface imports fatty acids (FAs). Blockage of import reversibly arrested parasite schizogony. In 11Met-O-Met11 mediated denaturation resistant PfP2 tetramer, the 12/53Cys-Cys12/53 redox switch regulates the binding and release of FAs based on oxidized/reduced state of disulfide linkages. This mechanistic insight of FAs import through PfP2 tetramer reveals a unique regulation of nuclear division at the onset of schizogony.
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Affiliation(s)
- Sudipta Das
- Division of infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C Mullick Road, Jadavpur, Kolkata 700032, India
| | - Anwesa Manna
- Division of infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C Mullick Road, Jadavpur, Kolkata 700032, India
| | - Oindrila Majumdar
- Division of infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C Mullick Road, Jadavpur, Kolkata 700032, India
| | - Lena Dhara
- Division of infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C Mullick Road, Jadavpur, Kolkata 700032, India
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Das S, Roy B, Chakrabarty S. Non-ribosomal insights into ribosomal P2 protein in Plasmodium falciparum-infected erythrocytes. Microbiologyopen 2021; 10:e1188. [PMID: 34459544 PMCID: PMC8380560 DOI: 10.1002/mbo3.1188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 04/10/2021] [Indexed: 11/12/2022] Open
Abstract
The enormous complexity of the eukaryotic ribosome has been a real challenge in unlocking the mechanistic aspects of its amazing molecular function during mRNA translation and many non‐canonical activities of ribosomal proteins in eukaryotic cells. While exploring the uncanny nature of ribosomal P proteins in malaria parasites Plasmodium falciparum, the 60S stalk ribosomal P2 protein has been shown to get exported to the infected erythrocyte (IE) surface as an SDS‐resistant oligomer during the early to the mid‐trophozoite stage. Inhibiting IE surface P2 either by monoclonal antibody or through genetic knockdown resulted in nuclear division arrest of the parasite. This strange and serendipitous finding has led us to explore more about un‐canonical cell biology and the structural involvement of P2 protein in Plasmodium in the search for a novel biochemical role during parasite propagation in the human host.
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Affiliation(s)
- Sudipta Das
- Asymmetric Cell Division Laboratory, Division of Infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Bhaskar Roy
- Asymmetric Cell Division Laboratory, Division of Infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Saswata Chakrabarty
- Asymmetric Cell Division Laboratory, Division of Infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, Kolkata, India
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3
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Molecular study of binding of Plasmodium ribosomal protein P2 to erythrocytes. Biochimie 2020; 176:181-191. [PMID: 32717409 DOI: 10.1016/j.biochi.2020.07.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/13/2020] [Accepted: 07/09/2020] [Indexed: 11/23/2022]
Abstract
The ribosomal protein P2 of Plasmodium falciparum, (PfP2), performs certain unique extra-ribosomal functions. During the few hours of cell-division, PfP2 protein moves to the external surface of the infected erythrocytes (IE) as an SDS-resistant oligomer, and at that stage treatment with specific anti- PfP2 antibodies results in an arrest of the parasite cell-division. Amongst the oligomeric forms of PfP2, mainly the homo-tetramer is peripherally anchored on the external surface of the IE. To study the anchoring of PfP2 tetramer on IE-surface, we have explored the binding properties of PfP2 protein. Using NMR and erythrocyte pull-down studies, here we report that the homo-tetrameric PfP2 protein interacted specifically with erythrocytes and not leukocytes. The hydrophobic N-terminal 72 amino acid region is the major interacting domain. The binding of P2 to RBCs was neuraminidase resistant, but trypsin sensitive. The RBC binding was exclusive to the Plasmodium PfP2 protein as even the homologous protein of the closely related Apicomplexan parasite Toxoplasma gondii TgP2 protein did not interact with erythrocytes. Pull down assays, immunoprecipitation and mass spectrometry data showed that erythrocytic Band 3 protein is a possible interactor of Plasmodium PfP2 protein on the erythrocyte surface.
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4
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Danielson TA, Stine JM, Dar TA, Briknarova K, Bowler BE. Effect of an Imposed Contact on Secondary Structure in the Denatured State of Yeast Iso-1-cytochrome c. Biochemistry 2017; 56:6662-6676. [PMID: 29148740 DOI: 10.1021/acs.biochem.7b01002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
There is considerable evidence that long-range interactions stabilize residual protein structure under denaturing conditions. However, evaluation of the effect of a specific contact on structure in the denatured state has been difficult. Iso-1-cytochrome c variants with a Lys54 → His mutation form a particularly stable His-heme loop in the denatured state, suggestive of loop-induced residual structure. We have used multidimensional nuclear magnetic resonance methods to assign 1H and 15N backbone amide and 13C backbone and side chain chemical shifts in the denatured state of iso-1-cytochrome c carrying the Lys54 → His mutation in 3 and 6 M guanidine hydrochloride and at both pH 6.4, where the His54-heme loop is formed, and pH 3.6, where the His54-heme loop is broken. Using the secondary structure propensity score, with the 6 M guanidine hydrochloride chemical shift data as a random coil reference state for data collected in 3 M guanidine hydrochloride, we found residual helical structure in the denatured state for the 60s helix and the C-terminal helix, but not in the N-terminal helix in the presence or absence of the His54-heme loop. Non-native helical structure is observed in two regions that form Ω-loops in the native state. There is more residual helical structure in the C-terminal helix at pH 6.4 when the loop is formed. Loop formation also appears to stabilize helical structure near His54, consistent with induction of helical structure observed when His-heme bonds form in heme-peptide model systems. The results are discussed in the context of the folding mechanism of cytochrome c.
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Affiliation(s)
- Travis A Danielson
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States
| | - Jessica M Stine
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States
| | - Tanveer A Dar
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States
| | - Klara Briknarova
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States.,Center for Biomolecular Structure and Dynamics, University of Montana , Missoula, Montana 59812, United States
| | - Bruce E Bowler
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States.,Center for Biomolecular Structure and Dynamics, University of Montana , Missoula, Montana 59812, United States
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Sakurai K, Yagi M, Konuma T, Takahashi S, Nishimura C, Goto Y. Non-Native α-Helices in the Initial Folding Intermediate Facilitate the Ordered Assembly of the β-Barrel in β-Lactoglobulin. Biochemistry 2017; 56:4799-4807. [PMID: 28795569 DOI: 10.1021/acs.biochem.7b00458] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The roles of non-native α-helices frequently observed in the initial folding stage of β-sheet proteins have been examined for many years. We herein investigated the residue-level structures of several mutants of bovine β-lactoglobulin (βLG) in quenched-flow pH-pulse labeling experiments. βLG assumes a collapsed intermediate with a non-native α-helical structure (I0) in the early stage of folding, although its native form is predominantly composed of β-structures. The protection profile in I0 of pseudo-wild type (WT*) βLG was found to deviate from the pattern of the "average area buried upon folding" (AABUF). In particular, the level of protection at the region of strand A, at which non-native α-helices form in the I0 state, was significantly low compared to AABUF. G17E, the mutant with an increased helical propensity, showed a similar protection pattern. In contrast, the protection pattern for I0 of E44L, the mutant with an increased β-sheet propensity, was distinct from that of WT* and resembled the AABUF pattern. Transverse relaxation measurements demonstrated that the positions of the residual structures in the unfolded states of these mutants were consistent with those of the protected residues in the respective I0 states. On the basis of the slower conversion of I0 to the native state for E44L to that for WT*, non-native α-helices facilitate the ordered assembly of the β-barrel by preventing interactions that trap folding.
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Affiliation(s)
- Kazumasa Sakurai
- High Pressure Protein Research Center, Institute of Advanced Technology, Kindai University , 930 Nishimitani, Kinokawa, Wakayama 649-6493, Japan.,Institute for Protein Research, Osaka University , 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Masanori Yagi
- Research Institute for Microbial Diseases, Osaka University , 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tsuyoshi Konuma
- Institute for Protein Research, Osaka University , 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Satoshi Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Chiaki Nishimura
- Faculty of Pharmaceutical Sciences, Teikyo Heisei University , 4-21-2 Nakano, Nakano-ku, Tokyo 164-8530, Japan
| | - Yuji Goto
- Institute for Protein Research, Osaka University , 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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Mishra P, Choudhary S, Hosur RV. Ribosomal Protein P2 from apicomplexan parasite Toxoplasma gondii is intrinsically a molten globule. Biophys Chem 2015; 200-201:27-33. [DOI: 10.1016/j.bpc.2015.03.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 03/20/2015] [Accepted: 03/22/2015] [Indexed: 11/30/2022]
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7
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Mishra P, Choudhary S, Mukherjee S, Sengupta D, Sharma S, Hosur RV. Molten globule nature of Plasmodium falciparum P2 homo-tetramer. Biochem Biophys Rep 2015; 1:97-107. [PMID: 29124138 PMCID: PMC5668626 DOI: 10.1016/j.bbrep.2015.03.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 03/20/2015] [Accepted: 03/23/2015] [Indexed: 11/24/2022] Open
Abstract
The P2 protein in Plasmodium falciparum has a high tendency to oligomerize, which seems to drive many of its non-ribosomal functions. During nuclear division of the parasite inside RBC, P2 translocates to the RBC surface as a tetramer. From a systematic study using variety of biophysical techniques, NMR spectral characteristics and relaxation dispersion measurements under different conditions of pH and/or urea concentrations, we deduce that (i) PfP2, an almost entirely helical protein, forms a molten globule monomer at low pH, (ii) at physiological pH, and at micro-molar concentrations, PfP2 is a stable tetramer wherein two dimmers associate sideways with close packing of helices at the interface, and (iii) the molten globule characteristic of the monomer is preserved in the tetramer. This dynamism in the structure of PfP2 may have functional implications since it is known that different kinds of oligomers are transiently formed in the parasite. Plasmodium falciparum P2 (PfP2) is a molten globule. PfP2 is a monomer at pH 2 and a tetramer at physiological pH. The step-wise assembly of the tetramer has been elucidated. A model structure for the PfP2-tetramer has been derived.
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Affiliation(s)
- Pushpa Mishra
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400005, Maharashtra, India
| | - Sinjan Choudhary
- UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Mumbai 400098, Maharashtra, India
| | - Sujoy Mukherjee
- Structural Biology and Bioinformatics Division, Indian Institute of Chemical Biology, Kolkata 700032, West Bengal, India
| | - Disha Sengupta
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400005, Maharashtra, India
| | - Shobhona Sharma
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400005, Maharashtra, India
| | - Ramakrishna V Hosur
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400005, Maharashtra, India.,UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Mumbai 400098, Maharashtra, India
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Wawiórka L, Krokowski D, Gordiyenko Y, Krowarsch D, Robinson CV, Adam I, Grankowski N, Tchórzewski M. In vivo formation of Plasmodium falciparum ribosomal stalk - a unique mode of assembly without stable heterodimeric intermediates. Biochim Biophys Acta Gen Subj 2014; 1850:150-8. [PMID: 25450178 DOI: 10.1016/j.bbagen.2014.10.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 09/19/2014] [Accepted: 10/15/2014] [Indexed: 11/25/2022]
Abstract
BACKGROUND The ribosomal stalk composed of P-proteins constitutes a structure on the large ribosomal particle responsible for recruitment of translation factors and stimulation of factor-dependent GTP hydrolysis during translation. The main components of the stalk are P-proteins, which form a pentamer. Despite the conserved basic function of the stalk, the P-proteins do not form a uniform entity, displaying heterogeneity in the primary structure across the eukaryotic lineage. The P-proteins from protozoan parasites are among the most evolutionarily divergent stalk proteins. METHODS We have assembled P-stalk complex of Plasmodium falciparum in vivo in bacterial system using tricistronic expression cassette and provided its characteristics by biochemical and biophysical methods. RESULTS All three individual P-proteins, namely uL10/P0, P1 and P2, are indispensable for acquisition of a stable structure of the P stalk complex and the pentameric uL10/P0-(P1-P2)₂form represents the most favorable architecture for parasite P-proteins. CONCLUSION The formation of P. falciparum P-stalk is driven by trilateral interaction between individual elements which represents unique mode of assembling, without stable P1-P2 heterodimeric intermediate. GENERAL SIGNIFICANCE On the basis of our mass-spectrometry analysis supported by the bacterial two-hybrid assay and biophysical analyses, a unique pathway of the parasite stalk assembling has been proposed. We suggest that the absence of P1/P2 heterodimer, and the formation of a stable pentamer in the presence of all three proteins, indicate a one-step formation to be the main pathway for the vital ribosomal stalk assembly, whereas the P2 homo-oligomer may represent an off-pathway product with physiologically important nonribosomal role.
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Affiliation(s)
- Leszek Wawiórka
- Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland
| | - Dawid Krokowski
- Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland
| | - Yuliya Gordiyenko
- Department of Chemistry, University of Oxford, South Parks Rd, Oxford OX1 3QZ, UK
| | - Daniel Krowarsch
- Department of Protein Biotechnology, Faculty of Biotechnology, University of Wroclaw, Tamka 2, 50-137 Wroclaw, Poland
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, South Parks Rd, Oxford OX1 3QZ, UK
| | - Ishag Adam
- Department of Obstetrics & Gynecology, Faculty of Medicine, AlKaser Street, University of Khartoum, Khartoum, Sudan
| | - Nikodem Grankowski
- Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland
| | - Marek Tchórzewski
- Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
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Sudarsan R, Chopra RK, Khan MA, Sharma S. Ribosomal protein P2 localizes to the parasite zoite-surface and is a target for invasion inhibitory antibodies in Toxoplasma gondii and Plasmodium falciparum. Parasitol Int 2014; 64:43-9. [PMID: 25280460 DOI: 10.1016/j.parint.2014.08.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 08/14/2014] [Accepted: 08/30/2014] [Indexed: 10/24/2022]
Abstract
In the malarial parasite Plasmodium falciparum, the conserved ribosomal stalk protein P2 (PfP2) exhibits extra-ribosomal stage-specific oligomerization and trafficking to the host red cell membrane. Antibodies directed against PfP2 arrested cell division. We sought to examine whether P2 from a closely related Apicomplexan parasite, Toxoplasma gondii, exhibits similar properties in terms of its oligomeric status as well as such unique host-cell localization. Circular dichroism spectroscopy of recombinant P2 from T. gondii (TgP2) showed a structure similar to that of PfP2, but unlike PfP2, which forms SDS- and DTT-resistant oligomers, TgP2 exhibited only a weak SDS-resistant dimerization. Also, unlike PfP2 localization to the infected erythrocyte surface, TgP2 did not localize to the host membrane in T. gondii infected human foreskin fibroblast cells. However, P2 protein was detected on the free tachyzoite surface, corroborated by localization of epitope-tagged P2 transfected in T. gondii. The presence of P2 on the surface of P. falciparum merozoites was also observed, and specific antibodies raised against the P2 protein blocked both T. gondii and P. falciparum zoite invasion of the host cells. Thus, although certain moonlighting functions of the acidic ribosomal protein P2 are different amongst P. falciparum and T. gondii, the P2 protein localizes to the surface of the invasive zoite form, and appears to constitute a potential target for host cell invasion inhibition in both the Apicomplexan infections.
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Affiliation(s)
- Rajagopal Sudarsan
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India.
| | - Reshma Korde Chopra
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Mudassar Ali Khan
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Shobhona Sharma
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
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10
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Hu M, Li L, Chao J, Zhao Y, Zhang Z, Liang A. The acidic ribosomal protein P2 from Euplotes octocarinatus is phosphorylated at its N-terminal domain. Biochem Cell Biol 2014; 92:23-32. [PMID: 24471915 DOI: 10.1139/bcb-2013-0063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The eukaryotic acid ribosomal P0, P1, and P2 proteins share a conserved flexible C-terminal tail that is rich in acidic residues, which are involved in the interaction with elongation factor 2 during protein synthesis. Our previous work suggested that the acidic ribosomal P proteins from Euplotes octocarinatus have a special C-terminal domain. To further understand this characteristic feature, both P2 and elongation factor 2 from E. octocarinatus were overexpressed, for the first time, in Escherichia coli in this study. GST pull-down assay indicated that P2 protein from E. octocarinatus (EoP2) interacted specifically with the N-terminal domain of elongation factor 2 from E. octocarinatus (EoEF-2) in vitro. The interacting part of EoP2 is in the C-terminal domains, consistent with the observation in other organisms. Phosphorylation of the recombinant EoP2 was performed in vitro using multiple methods such as (31)P-NMR spectroscopy, native PAGE, and Phos-tag(TM) SDS-PAGE. Results showed that ribosomal protein EoP2 was phosphorylated by casein kinase II at serine 21 located at the N terminus. This phosphorylation site identified in EoP2 is quite different from that of P2 from other organisms, in which the phosphorylation site is located in the conserved C-terminal region.
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Affiliation(s)
- Miaoqing Hu
- a Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
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11
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Salt-Induced Changes in the Subunit Structure of the Bacillus stearothermophilusLipoate Acetyltransferase. Biosci Biotechnol Biochem 2013; 77:1637-44. [DOI: 10.1271/bbb.130161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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12
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Mishra P, Sharma S, Hosur RV. Residue level description of In vivo self-association ofPlasmodium falciparumP2. J Biomol Struct Dyn 2013; 32:602-12. [PMID: 23581826 DOI: 10.1080/07391102.2013.782827] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Pushpa Mishra
- a Department of Chemical Sciences , Tata Institute of Fundamental Research , Mumbai , India
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13
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Das S, Sudarsan R, Sivakami S, Sharma S. Erythrocytic stage-dependent regulation of oligomerization of Plasmodium ribosomal protein P2. J Biol Chem 2012; 287:41499-513. [PMID: 23060439 DOI: 10.1074/jbc.m112.384388] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The eukaryotic 60 S-ribosomal stalk consists of P0, P1, and P2 proteins, which associate in a pentameric structure (P1(2)-P0-P2(2)). The Plasmodium falciparum protein P2 (PfP2) appears to play nonribosomal roles. It gets exported to the infected erythrocyte (IE) surface at 30 h post-merozoite invasion (PMI), concomitant with extensive oligomerization. Here we present certain biophysical properties of PfP2. Recombinant P2 (rPfP2) protein showed SDS-resistant oligomerization, which could be significantly abolished under reducing conditions. However, the protein continued to oligomerize even when both cysteine residues were mutated, and with up to 40 amino acids (aa) deleted from the C-terminal end. CD analysis of P2 showed largely α-helical and random coil domains. The SDS- and DTT-resistant oligomerization was studied further as it occurred in a development-specific manner in Plasmodium. In a synchronized erythrocytic culture of P. falciparum, the PfP2 protein was detected as part of the ribosomal complex (∼96 kDa) at 18 and 30 h PMI, and was SDS sensitive. However, at 30 h, large amounts of SDS-sensitive aggregates of >600 kDa were also seen. At 30 h PMI, each of the parasites, IE cytosol and IE ghost contained 60-80-kDa PfP2 complexes, which resolved to a single 65-kDa species on SDS-PAGE. Tetramethylrhodamine-labeled rPfP2 protein exhibited DTT- and SDS-resistant oligomerization when treated with P. falciparum parasite extracts only from 24 to 36 h PMI, and multiple proteins appeared to be required for this oligomerization. Understanding the regulation of oligomerization of PfP2 may help in the elucidation of the novel structure-function relationship in the export of PfP2 to the red cell surface.
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Affiliation(s)
- Sudipta Das
- Department of Biological Sciences, Tata Institute of Fundamental Research, 400005 Mumbai, India
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