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Cilek N, Ugurel E, Goksel E, Yalcin O. Signaling mechanisms in red blood cells: A view through the protein phosphorylation and deformability. J Cell Physiol 2024; 239:e30958. [PMID: 36748950 DOI: 10.1002/jcp.30958] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 01/07/2023] [Accepted: 01/19/2023] [Indexed: 02/08/2023]
Abstract
Intracellular signaling mechanisms in red blood cells (RBCs) involve various protein kinases and phosphatases and enable rapid adaptive responses to hypoxia, metabolic requirements, oxidative stress, or shear stress by regulating the physiological properties of the cell. Protein phosphorylation is a ubiquitous mechanism for intracellular signal transduction, volume regulation, and cytoskeletal organization in RBCs. Spectrin-based cytoskeleton connects integral membrane proteins, band 3 and glycophorin C to junctional proteins, ankyrin and Protein 4.1. Phosphorylation leads to a conformational change in the protein structure, weakening the interactions between proteins in the cytoskeletal network that confers a more flexible nature for the RBC membrane. The structural organization of the membrane and the cytoskeleton determines RBC deformability that allows cells to change their ability to deform under shear stress to pass through narrow capillaries. The shear stress sensing mechanisms and oxygenation-deoxygenation transitions regulate cell volume and mechanical properties of the membrane through the activation of ion transporters and specific phosphorylation events mediated by signal transduction. In this review, we summarize the roles of Protein kinase C, cAMP-Protein kinase A, cGMP-nitric oxide, RhoGTPase, and MAP/ERK pathways in the modulation of RBC deformability in both healthy and disease states. We emphasize that targeting signaling elements may be a therapeutic strategy for the treatment of hemoglobinopathies or channelopathies. We expect the present review will provide additional insights into RBC responses to shear stress and hypoxia via signaling mechanisms and shed light on the current and novel treatment options for pathophysiological conditions.
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Affiliation(s)
- Neslihan Cilek
- Research Center for Translational Medicine (KUTTAM), Koc University, Istanbul, Turkey
- School of Medicine, Koc University, Istanbul, Turkey
- Graduate School of Health Sciences, Koc University, Istanbul, Turkey
| | - Elif Ugurel
- Research Center for Translational Medicine (KUTTAM), Koc University, Istanbul, Turkey
- School of Medicine, Koc University, Istanbul, Turkey
| | - Evrim Goksel
- Research Center for Translational Medicine (KUTTAM), Koc University, Istanbul, Turkey
- School of Medicine, Koc University, Istanbul, Turkey
- Graduate School of Health Sciences, Koc University, Istanbul, Turkey
| | - Ozlem Yalcin
- Research Center for Translational Medicine (KUTTAM), Koc University, Istanbul, Turkey
- School of Medicine, Koc University, Istanbul, Turkey
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2
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Kim HJ, Kim WJ, Ryoo HM. Post-Translational Regulations of Transcriptional Activity of RUNX2. Mol Cells 2020; 43:160-167. [PMID: 31878768 PMCID: PMC7057842 DOI: 10.14348/molcells.2019.0247] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 12/04/2019] [Indexed: 01/20/2023] Open
Abstract
Runt-related transcription factor 2 (RUNX2) is a key transcription factor for bone formation and osteoblast differentiation. Various signaling pathways and mechanisms that regulate the expression and transcriptional activity of RUNX2 have been thoroughly investigated since the involvement of RUNX2 was first reported in bone formation. As the regulation of Runx2 expression by extracellular signals has recently been reviewed, this review focuses on the regulation of post-translational RUNX2 activity. Transcriptional activity of RUNX2 is regulated at the post-translational level by various enzymes including kinases, acetyl transferases, deacetylases, ubiquitin E3 ligases, and prolyl isomerases. We describe a sequential and linear causality between post-translational modifications of RUNX2 by these enzymes. RUNX2 is one of the most important osteogenic transcription factors; however, it is not a suitable drug target. Here, we suggest enzymes that directly regulate the stability and/or transcriptional activity of RUNX2 at a post-translational level as effective drug targets for treating bone diseases.
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Affiliation(s)
- Hyun-Jung Kim
- Department of Molecular Genetics & Dental Pharmacology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 08826, Korea
| | - Woo-Jin Kim
- Department of Molecular Genetics & Dental Pharmacology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 08826, Korea
| | - Hyun-Mo Ryoo
- Department of Molecular Genetics & Dental Pharmacology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 08826, Korea
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3
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Zhao L, Ouyang Y, Li Q, Zhang Z. Modulation of p53 N-terminal transactivation domain 2 conformation ensemble and kinetics by phosphorylation. J Biomol Struct Dyn 2019; 38:2613-2623. [DOI: 10.1080/07391102.2019.1637784] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Likun Zhao
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yanhua Ouyang
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Qian Li
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Zhuqing Zhang
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
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4
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Song T, Wang P, Yu X, Wang A, Chai G, Fan Y, Zhang Z. Systems analysis of phosphorylation-regulated Bcl-2 interactions establishes a model to reconcile the controversy over the significance of Bcl-2 phosphorylation. Br J Pharmacol 2019; 176:491-504. [PMID: 30500985 PMCID: PMC6329625 DOI: 10.1111/bph.14555] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 10/23/2018] [Accepted: 10/25/2018] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE The biological significance of the multi-site phosphorylation of Bcl-2 at its loop region (T69, S70 and S87) has remained controversial for decades. This is a major obstacle for understanding apoptosis and anti-tumour drug development. EXPERIMENTAL APPROACH We established a mathematical model into which a phosphorylation and de-phosphorylation process of Bcl-2 was integrated. Paclitaxel-treated breast cancer cells were used as experimental models. Changes in the kinetics of binding with its critical partners, induced by phosphorylation of Bcl-2 were experimentally obtained by surface plasmon resonance, using a phosphorylation-mimicking mutant EEE-Bcl-2 (T69E, S70E and S87E). KEY RESULTS Mathematical simulations combined with experimental validation showed that phosphorylation regulates Bcl-2 with different dynamics depending on the extent of Bcl-2 phosphorylation and the phosphorylated Bcl-2-induced changes in binding kinetics. In response to Bcl-2 homology 3 (BH3)-only protein Bmf stress, Bcl-2 phosphorylation switched from diminishing to enhancing the Bcl-2 anti-apoptotic ability with increased phosphorylation of Bcl-2, and the turning point was 50% Bcl-2 phosphorylation induced by 0.2 μM paclitaxel treatment. In contrast, Bcl-2 phosphorylation enhanced the anti-apoptotic ability of Bcl-2 towards other BH3-only proteins Bim, Bad and Puma, throughout the entire phosphorylation procedure. CONCLUSIONS AND IMPLICATIONS The model could accurately predict the effects of anti-tumour drugs that involve the Bcl-2 family pathway, as shown with ABT-199 or etoposide.
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Affiliation(s)
- Ting Song
- State Key Laboratory of Fine Chemicals, School of ChemistryDalian University of TechnologyDalianChina
| | - Peiran Wang
- State Key Laboratory of Fine Chemicals, School of ChemistryDalian University of TechnologyDalianChina
| | - Xiaoyan Yu
- School of Life Science and TechnologyDalian University of TechnologyDalianChina
| | - Anhui Wang
- School of Innovation ExperimentDalian University of TechnologyDalianChina
| | - Gaobo Chai
- School of Life Science and TechnologyDalian University of TechnologyDalianChina
| | - Yudan Fan
- School of Life Science and TechnologyDalian University of TechnologyDalianChina
| | - Zhichao Zhang
- State Key Laboratory of Fine Chemicals, School of ChemistryDalian University of TechnologyDalianChina
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5
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Miears HL, Gruber DR, Horvath NM, Antos JM, Young J, Sigurjonsson JP, Klem ML, Rosenkranz EA, Okon M, McKnight CJ, Vugmeyster L, Smirnov SL. Plant Villin Headpiece Domain Demonstrates a Novel Surface Charge Pattern and High Affinity for F-Actin. Biochemistry 2018; 57:1690-1701. [PMID: 29444403 DOI: 10.1021/acs.biochem.7b00856] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Plants utilize multiple isoforms of villin, an F-actin regulating protein with an N-terminal gelsolin-like core and a distinct C-terminal headpiece domain. Unlike their vertebrate homologues, plant villins have a much longer linker polypeptide connecting the core and headpiece. Moreover, the linker-headpiece connection region in plant villins lacks sequence homology to the vertebrate villin sequences. It is unknown to what extent the plant villin headpiece structure and function resemble those of the well-studied vertebrate counterparts. Here we present the first solution NMR structure and backbone dynamics characterization of a headpiece from plants, villin isoform 4 from Arabidopsis thaliana. The villin 4 headpiece is a 63-residue domain (V4HP63) that adopts a typical headpiece fold with an aromatics core and a tryptophan-centered hydrophobic cap within its C-terminal subdomain. However, V4HP63 has a distinct N-terminal subdomain fold as well as a novel, high mobility loop due to the insertion of serine residue in the canonical sequence that follows the variable length loop in headpiece sequences. The domain binds actin filaments with micromolar affinity, like the vertebrate analogues. However, the V4HP63 surface charge pattern is novel and lacks certain features previously thought necessary for high-affinity F-actin binding. Utilizing the updated criteria for strong F-actin binding, we predict that the headpiece domains of all other villin isoforms in A. thaliana have high affinity for F-actin.
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Affiliation(s)
- Heather L Miears
- Department of Chemistry , Western Washington University , 516 High Street , Bellingham , Washington 98225-9150 , United States
| | - David R Gruber
- Department of Chemistry , Western Washington University , 516 High Street , Bellingham , Washington 98225-9150 , United States
| | - Nicholas M Horvath
- Department of Chemistry , Western Washington University , 516 High Street , Bellingham , Washington 98225-9150 , United States
| | - John M Antos
- Department of Chemistry , Western Washington University , 516 High Street , Bellingham , Washington 98225-9150 , United States
| | - Jeff Young
- Department of Biology , Western Washington University , 516 High Street , Bellingham , Washington 98225-9160 , United States
| | - Johann P Sigurjonsson
- Department of Chemistry , Western Washington University , 516 High Street , Bellingham , Washington 98225-9150 , United States
| | - Maya L Klem
- Department of Chemistry , Western Washington University , 516 High Street , Bellingham , Washington 98225-9150 , United States
| | - Erin A Rosenkranz
- Department of Chemistry , Western Washington University , 516 High Street , Bellingham , Washington 98225-9150 , United States
| | - Mark Okon
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories , University of British Columbia , Vancouver , British Columbia V6T 1Z3 , Canada
| | - C James McKnight
- Department of Physiology and Biophysics , Boston University School of Medicine , 700 Albany Street , Boston , Massachusetts 02118-2526 , United States
| | - Liliya Vugmeyster
- Department of Chemistry , University of Colorado at Denver , Denver , Colorado 80204 , United States
| | - Serge L Smirnov
- Department of Chemistry , Western Washington University , 516 High Street , Bellingham , Washington 98225-9150 , United States
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6
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Meng H, Fitzgerald MC. Proteome-Wide Characterization of Phosphorylation-Induced Conformational Changes in Breast Cancer. J Proteome Res 2018; 17:1129-1137. [PMID: 29332387 DOI: 10.1021/acs.jproteome.7b00795] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Because of the close link between protein function and protein folding stability, knowledge about phosphorylation-induced protein folding stability changes can lead to a better understanding of the functional effects of protein phosphorylation. Here, the stability of proteins from rates of oxidation (SPROX) and limited proteolysis (LiP) techniques are used to compare the conformational properties of proteins in two MCF-7 cell lysates including one that was and one that was not dephosphorylated with alkaline phosphatase. A total of 168 and 251 protein hits were identified with dephosphorylation-induced stability changes using the SPROX and LiP techniques, respectively. Many protein hits are previously known to be differentially phosphorylated or differentially stabilized in different human breast cancer subtypes, suggesting that the phosphorylation-induced stability changes detected in this work are disease related. The SPROX hits were enriched in proteins with aminoacyl-tRNA ligase activity. These enriched protein hits included many aminoacyl-tRNA synthetases (aaRSs), which are known from previous studies to have their catalytic activity modulated by phosphorylation. The SPROX results revealed that the magnitudes of the destabilizing effects of dephoshporylation on the different aaRSs were directly correlated with their previously reported aminoacylation activity change upon dephosphorylation. This substantiates the close link between protein folding and function.
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Affiliation(s)
- He Meng
- Department of Chemistry, Duke University , Durham, North Carolina 27708, United States
| | - Michael C Fitzgerald
- Department of Chemistry, Duke University , Durham, North Carolina 27708, United States
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7
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Dahal L, Shammas SL, Clarke J. Phosphorylation of the IDP KID Modulates Affinity for KIX by Increasing the Lifetime of the Complex. Biophys J 2018; 113:2706-2712. [PMID: 29262363 PMCID: PMC5770967 DOI: 10.1016/j.bpj.2017.10.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 10/04/2017] [Accepted: 10/10/2017] [Indexed: 11/17/2022] Open
Abstract
Intrinsically disordered proteins (IDPs) are known to undergo a range of posttranslational modifications, but by what mechanism do such modifications affect the binding of an IDP to its partner protein? We investigate this question using one such IDP, the kinase inducible domain (KID) of the transcription factor CREB, which interacts with the KIX domain of CREB-binding protein upon phosphorylation. As with many other IDPs, KID undergoes coupled folding and binding to form α-helical structure upon interacting with KIX. This single site phosphorylation plays an important role in the control of transcriptional activation in vivo. Here we show that, contrary to expectation, phosphorylation has no effect on association rates—unphosphorylated KID binds just as rapidly as pKID, the phosphorylated form—but rather, acts by increasing the lifetime of the complex. We propose that by controlling the lifetime of the bound complex of pKID:KIX via altering the dissociation rate, phosphorylation can facilitate effective control of transcription regulation.
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Affiliation(s)
- Liza Dahal
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Sarah L Shammas
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
| | - Jane Clarke
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
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8
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Lin B, Harris DR, Kirkman LMD, Perez AM, Qian Y, Schermerhorn JT, Hong MY, Winston DS, Xu L, Brandt GS. FIKK Kinase, a Ser/Thr Kinase Important to Malaria Parasites, Is Inhibited by Tyrosine Kinase Inhibitors. ACS OMEGA 2017; 2:6605-6612. [PMID: 30023525 PMCID: PMC6044879 DOI: 10.1021/acsomega.7b00997] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 09/27/2017] [Indexed: 06/08/2023]
Abstract
A relatively high-affinity inhibitor of FIKK kinase from the malaria parasite Plasmodium vivax was identified by in vitro assay of recombinant kinase. The FIKK kinase family is unique to parasitic organisms of the Apicomplexan order and has been shown to be critical in malaria parasites. The recombinant kinase domain was expressed and screened against a small molecule library, revealing a number of tyrosine kinase inhibitors that block FIKK kinase activity. A family of tyrphostins was further investigated, to begin exploring the FIKK kinase pharmacophore. Finally, emodin was identified as a relatively high-affinity FIKK kinase inhibitor, identifying this family of anthraquinones as potential lead compounds for the development of antimalarials targeting the FIKK kinase.
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9
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Lin BC, Harris DR, Kirkman LMD, Perez AM, Qian Y, Schermerhorn JT, Hong MY, Winston DS, Xu L, Lieber AM, Hamilton M, Brandt GS. The anthraquinone emodin inhibits the non-exported FIKK kinase from Plasmodium falciparum. Bioorg Chem 2017; 75:217-223. [PMID: 28987877 DOI: 10.1016/j.bioorg.2017.09.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 09/13/2017] [Accepted: 09/15/2017] [Indexed: 01/08/2023]
Abstract
The FIKK family of kinases is unique to parasites of the Apicomplexan order, which includes all malaria parasites. Plasmodium falciparum, the most virulent form of human malaria, has a family of 19 FIKK kinases, most of which are exported into the host red blood cell during malaria infection. Here, we confirm that FIKK 8 is a non-exported member of the FIKK kinase family. Through expression and purification of the recombinant kinase domain, we establish that emodin is a relatively high-affinity (IC50=2μM) inhibitor of PfFk8. Closely related anthraquinones do not inhibit PfFk8, suggesting that the particular substitution pattern of emodin is critical to the inhibitory pharmacophore. This first report of a P. falciparum FIKK kinase inhibitor lays the groundwork for developing specific inhibitors of the various members of the FIKK kinase family in order to probe their physiological function.
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Affiliation(s)
- Benjamin C Lin
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Darcy R Harris
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Lucy M D Kirkman
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Astrid M Perez
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Yiwen Qian
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Janse T Schermerhorn
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Min Y Hong
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Dennis S Winston
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Lingyin Xu
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Alexander M Lieber
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Matthew Hamilton
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States
| | - Gabriel S Brandt
- Department of Chemistry, Franklin & Marshall College, Lancaster, PA, United States.
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10
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Park KR, An JY, Kang JY, Lee JG, Lee Y, Mun SA, Jun CD, Song WK, Eom SH. Structural mechanism underlying regulation of human EFhd2/Swiprosin-1 actin-bundling activity by Ser183 phosphorylation. Biochem Biophys Res Commun 2017; 483:442-448. [DOI: 10.1016/j.bbrc.2016.12.124] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 12/19/2016] [Indexed: 12/21/2022]
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11
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Chakrabarti A, Halder S, Karmakar S. Erythrocyte and platelet proteomics in hematological disorders. Proteomics Clin Appl 2016; 10:403-14. [PMID: 26611378 DOI: 10.1002/prca.201500080] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 10/26/2015] [Accepted: 11/19/2015] [Indexed: 12/20/2022]
Abstract
Erythrocytes undergo ineffective erythropoesis, hemolysis, and premature eryptosis in sickle cell disease and thalassemia. Abnormal hemoglobin variants associated with hemoglobinopathy lead to vesiculation, membrane instability, and loss of membrane asymmetry with exposal of phosphatidylserine. This potentiates thrombin generation resulting in activation of the coagulation cascade responsible for subclinical phenotypes. Platelet activation also results in the release of microparticles, which express and transfer functional receptors from platelet membrane, playing key roles in vascular reactivity and activation of intracellular signaling pathways. Over the last decade, proteomics had proven to be an important field of research in studies of blood and blood diseases. Blood cells and its fluidic components have been proven to be easy systems for studying differential expressions of proteins in hematological diseases encompassing hemoglobinopathies, different types of anemias, myeloproliferative disorders, and coagulopathies. Proteomic studies of erythrocytes and platelets reported from several groups have highlighted various factors that intersect the signaling networks in these anucleate systems. In this review, we have elaborated on the current scenario of anucleate blood cell proteomes in normal and diseased individuals and the cross-talk between the two major constituent cell types of circulating blood.
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Affiliation(s)
- Abhijit Chakrabarti
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Kolkata, India
| | - Suchismita Halder
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Kolkata, India
| | - Shilpita Karmakar
- Biophysics and Structural Genomics Division, Saha institute of Nuclear Physics, Kolkata, India
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12
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Kinetic modulation of a disordered protein domain by phosphorylation. Nat Commun 2014; 5:5272. [PMID: 25348080 DOI: 10.1038/ncomms6272] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 09/15/2014] [Indexed: 12/19/2022] Open
Abstract
Phosphorylation is a major post-translational mechanism of regulation that frequently targets disordered protein domains, but it remains unclear how phosphorylation modulates disordered states of proteins. Here we determine the kinetics and energetics of a disordered protein domain the kinase-inducible domain (KID) of the transcription factor CREB and that of its phosphorylated form pKID, using high-throughput molecular dynamic simulations. We identify the presence of a metastable, partially ordered state with a 60-fold slowdown in conformational kinetics that arises due to phosphorylation, kinetically stabilizing residues known to participate in an early binding intermediate. We show that this effect is only partially reconstituted by mutation to glutamate, indicating that the phosphate is uniquely required for the long-lived state to arise. This mechanism of kinetic modulation could be important for regulation beyond conformational equilibrium shifts.
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13
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Polonio-Vallon T, Krüger D, Hofmann TG. ShaPINg Cell Fate Upon DNA Damage: Role of Pin1 Isomerase in DNA Damage-Induced Cell Death and Repair. Front Oncol 2014; 4:148. [PMID: 24982848 PMCID: PMC4058901 DOI: 10.3389/fonc.2014.00148] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 05/28/2014] [Indexed: 01/04/2023] Open
Abstract
The peptidyl-prolyl cis/trans isomerase Pin1 acts as a molecular timer in proline-directed Ser/Thr kinase signaling and shapes cellular responses based on recognition of phosphorylation marks and implementing conformational changes in its substrates. Accordingly, Pin1 has been linked to numerous phosphorylation-controlled signaling pathways and cellular processes such as cell cycle progression, proliferation, and differentiation. In addition, Pin1 plays a pivotal role in DNA damage-triggered cell fate decisions. Whereas moderate DNA damage is balanced by DNA repair, cells confronted with massive genotoxic stress are eliminated by the induction of programed cell death or cellular senescence. In this review, we summarize and discuss the current knowledge on how Pin1 specifies cell fate through regulating key players of the apoptotic and the repair branch of the DNA-damage response.
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Affiliation(s)
- Tilman Polonio-Vallon
- Research Group Cellular Senescence, German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance , Heidelberg , Germany
| | - Daniel Krüger
- Research Group Cellular Senescence, German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance , Heidelberg , Germany
| | - Thomas G Hofmann
- Research Group Cellular Senescence, German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance , Heidelberg , Germany
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14
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Phosphorylation status of 72 kDa MMP-2 determines its structure and activity in response to peroxynitrite. PLoS One 2013; 8:e71794. [PMID: 24013357 PMCID: PMC3754950 DOI: 10.1371/journal.pone.0071794] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 07/03/2013] [Indexed: 11/19/2022] Open
Abstract
Matrix metalloproteinase-2 (MMP-2) is a key intra- and extra-cellular protease which contributes to several oxidative stress related pathologies. A molecular understanding of 72 kDa MMP-2 activity, directly mediated by S-glutathiolation of its cysteine residues in the presence of peroxynitrite (ONOO−) and by phosphorylation of its serine and threonine residues, is essential to develop new generation inhibitors of intracellular MMP-2. Within its propeptide and collagen binding domains there is an interesting juxtaposition of predicted phosphorylation sites with nearby cysteine residues which form disulfide bonds. However, the combined effect of these two post-translational modifications on MMP-2 activity has not been studied. The activity of human recombinant 72 kDa MMP-2 (hrMMP-2) following in vitro treatments was measured by troponin I proteolysis assay and a kinetic activity assay using a fluorogenic peptide substrate. ONOO− treatment in the presence of 30 µM glutathione resulted in concentration-dependent changes in MMP-2 activity, with 0.1–1 µM increasing up to twofold and 100 µM attenuating its activity. Dephosphorylation of MMP-2 with alkaline phosphatase markedly increased its activity by sevenfold, either with or without ONOO−. Dephosphorylation of MMP-2 also affected the conformational structure of the enzyme as revealed by circular dichroism studies, suggesting an increase in the proportion of α-helices and a decrease in β-strands compared to the phosphorylated form of MMP-2. These results suggest that ONOO− activation (at low µM) and inactivation (at high µM) of 72 kDa MMP-2, in the presence or absence of glutathione, is also influenced by its phosphorylation status. These insights into the role of post-translational modifications in the structure and activity of 72 kDa MMP-2 will aid in the development of inhibitors specifically targeting intracellular MMP-2.
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15
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Chen L, Brown JW, Mok YF, Hatters DM, McKnight CJ. The allosteric mechanism induced by protein kinase A (PKA) phosphorylation of dematin (band 4.9). J Biol Chem 2013; 288:8313-8320. [PMID: 23355471 DOI: 10.1074/jbc.m112.438861] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Dematin (band 4.9) is an F-actin binding and bundling protein best known for its role within red blood cells, where it both stabilizes as well as attaches the spectrin/actin cytoskeleton to the erythrocytic membrane. Here, we investigate the structural consequences of phosphorylating serine 381, a covalent modification that turns off F-actin bundling activity. In contrast to the canonical doctrine, in which phosphorylation of an intrinsically disordered region/protein confers affinity for another domain/protein, we found the converse to be true of dematin: phosphorylation of the well folded C-terminal villin-type headpiece confers affinity for its intrinsically disordered N-terminal core domain. We employed analytical ultracentrifugation to demonstrate that dematin is monomeric, in contrast to the prevailing view that it is trimeric. Next, using a series of truncation mutants, we verified that dematin has two F-actin binding sites, one in the core domain and the other in the headpiece domain. Although the phosphorylation-mimicking mutant, S381E, was incapable of bundling microfilaments, it retains the ability to bind F-actin. We found that a phosphorylation-mimicking mutant, S381E, eliminated the ability to bundle, but not bind F-actin filaments. Lastly, we show that the S381E point mutant caused the headpiece domain to associate with the core domain, leading us to the mechanism for cAMP-dependent kinase control of dematin's F-actin bundling activity: when unphosphorylated, dematin's two F-actin binding domains move independent of one another permitting them to bind different F-actin filaments. Phosphorylation causes these two domains to associate, forming a compact structure, and sterically eliminating one of these F-actin binding sites.
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Affiliation(s)
- Lin Chen
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Jeffrey W Brown
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Yee-Foong Mok
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 2010, Australia
| | - Danny M Hatters
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 2010, Australia
| | - C James McKnight
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118.
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Soderblom EJ, Thompson JW, Schwartz EA, Chiou E, Dubois LG, Moseley MA, Zennadi R. Proteomic analysis of ERK1/2-mediated human sickle red blood cell membrane protein phosphorylation. Clin Proteomics 2013; 10:1. [PMID: 23286773 PMCID: PMC3558407 DOI: 10.1186/1559-0275-10-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 12/19/2012] [Indexed: 11/10/2022] Open
Abstract
UNLABELLED BACKGROUND In sickle cell disease (SCD), the mitogen-activated protein kinase (MAPK) ERK1/2 is constitutively active and can be inducible by agonist-stimulation only in sickle but not in normal human red blood cells (RBCs). ERK1/2 is involved in activation of ICAM-4-mediated sickle RBC adhesion to the endothelium. However, other effects of the ERK1/2 activation in sickle RBCs leading to the complex SCD pathophysiology, such as alteration of RBC hemorheology are unknown. RESULTS To further characterize global ERK1/2-induced changes in membrane protein phosphorylation within human RBCs, a label-free quantitative phosphoproteomic analysis was applied to sickle and normal RBC membrane ghosts pre-treated with U0126, a specific inhibitor of MEK1/2, the upstream kinase of ERK1/2, in the presence or absence of recombinant active ERK2. Across eight unique treatment groups, 375 phosphopeptides from 155 phosphoproteins were quantified with an average technical coefficient of variation in peak intensity of 19.8%. Sickle RBC treatment with U0126 decreased thirty-six phosphopeptides from twenty-one phosphoproteins involved in regulation of not only RBC shape, flexibility, cell morphology maintenance and adhesion, but also glucose and glutamate transport, cAMP production, degradation of misfolded proteins and receptor ubiquitination. Glycophorin A was the most affected protein in sickle RBCs by this ERK1/2 pathway, which contained 12 unique phosphorylated peptides, suggesting that in addition to its effect on sickle RBC adhesion, increased glycophorin A phosphorylation via the ERK1/2 pathway may also affect glycophorin A interactions with band 3, which could result in decreases in both anion transport by band 3 and band 3 trafficking. The abundance of twelve of the thirty-six phosphopeptides were subsequently increased in normal RBCs co-incubated with recombinant ERK2 and therefore represent specific MEK1/2 phospho-inhibitory targets mediated via ERK2. CONCLUSIONS These findings expand upon the current model for the involvement of ERK1/2 signaling in RBCs. These findings also identify additional protein targets of this pathway other than the RBC adhesion molecule ICAM-4 and enhance the understanding of the mechanism of small molecule inhibitors of MEK/1/2/ERK1/2, which could be effective in ameliorating RBC hemorheology and adhesion, the hallmarks of SCD.
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Affiliation(s)
- Erik J Soderblom
- Division of Hematology and Duke Comprehensive Sickle Cell Center, Department of Medicine, Duke University Medical Center, Durham, NC, USA.
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Brown JW, Farelli JD, McKnight CJ. On the unyielding hydrophobic core of villin headpiece. Protein Sci 2012; 21:647-54. [PMID: 22467489 DOI: 10.1002/pro.2048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 02/09/2012] [Accepted: 02/13/2012] [Indexed: 11/06/2022]
Abstract
Villin headpiece (HP67) is a small, autonomously-folding domain that has become a model system for understanding the fundamental tenets governing protein folding. In this communication, we explore the role that Leu61 plays in the structure and stability of the construct. Deletion of Leu61 results in a completely unfolded protein that cannot be expressed in Escherichia coli. Omission of only the aliphatic leucine side chain (HP67 L61G) perturbed neither the backbone conformation nor the orientation of local hydrophobic side chains. As a result, a large, solvent-exposed hydrophobic pocket, a negative replica of the leucine side-chain, was created on the surface. The loss of the hydrophobic interface between leucine 61 and the hydrophobic pocket destabilized the construct by ~3.3 kcal/mol. Insertion of a single glycine residue immediately before Leu61 (HP67 L61[GL]) was also highly destabilizing and had the effect of altering the backbone conformation (α-helix to π-helix) in order to precisely preserve the wild-type position and conformation of all hydrophobic residues, including Leu61. In addition to demonstrating that the hydrophobic side-chain of Leu61 is critically important for the stability of villin headpiece, our results are consistent with the notion that the precise interactions present within the hydrophobic core, rather than the hydrogen bonds that define the secondary structure, specify a protein's fold.
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Affiliation(s)
- Jeffrey W Brown
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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Burton NM, Bruce LJ. Modelling the structure of the red cell membraneThis paper is one of a selection of papers published in a Special Issue entitled CSBMCB 53rd Annual Meeting — Membrane Proteins in Health and Disease, and has undergone the Journal’s usual peer review process. Biochem Cell Biol 2011; 89:200-15. [DOI: 10.1139/o10-154] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The red cell membrane has long been the focus of extensive study. The macromolecules embedded within the membrane carry the blood group antigens and perform many functions including the vital task of gas exchange. Links between the intramembrane macromolecules and the underlying cytoskeleton stabilize the biconcave morphology of the red cell and allow deformation during microvascular transit. Much is now known about the proteins of the red cell membrane and how they are organised. In many cases we have an understanding of which proteins are expressed, the number of each protein per cell, their oligomeric state(s), and how they are collected in large multi-protein complexes. However, our typical view of these structures is as cartoon shapes in schematic figures. In this study we have combined knowledge of the red cell membrane with a wealth of protein structure data from crystallography, NMR, and homology modelling to generate the first, tentative models of the complexes which link the membrane to the cytoskeleton. Measurement of the size of these complexes and comparison with known cytoskeletal distance parameters suggests the idea of interaction between the membrane complexes, which may have profound implications for understanding red cell function and deformation.
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Affiliation(s)
- Nicholas M. Burton
- School of Biochemistry, University of Bristol, BS8 1TD, UK
- Bristol Institute for Transfusion Sciences, N.H.S. Blood and Transplant, North Bristol Park, Filton, Bristol, BS34 7QH, UK
| | - Lesley J. Bruce
- School of Biochemistry, University of Bristol, BS8 1TD, UK
- Bristol Institute for Transfusion Sciences, N.H.S. Blood and Transplant, North Bristol Park, Filton, Bristol, BS34 7QH, UK
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Vugmeyster L, Ostrovsky D, Li Y. Comparison of fast backbone dynamics at amide nitrogen and carbonyl sites in dematin headpiece C-terminal domain and its S74E mutant. JOURNAL OF BIOMOLECULAR NMR 2010; 47:155-162. [PMID: 20396930 DOI: 10.1007/s10858-010-9417-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Accepted: 03/29/2010] [Indexed: 05/29/2023]
Abstract
We perform a detailed comparison of fast backbone dynamics probed at amide nitrogen versus carbonyl carbon sites for dematin headpiece C-terminal domain (DHP) and its S74E mutant (DHPS74E). Carbonyl dynamics is probed via auto-correlated longitudinal rates and transverse C'/C'-C(alpha) CSA/dipolar and C'/C'-N CSA/dipolar cross-correlated rates, while (15)N data are taken from a previous study. Resulting values of effective order parameters and internal correlation times support the conclusion that C' relaxation reports on a different subset of fast motions compared to those probed at N-H bond vectors in the same peptide planes. (13)C' order parameters are on the average 0.08 lower than (15)N order parameters with the exception of the flexible loop region in DHP. The reduction of mobility in the loop region upon the S74E mutation can be seen from the (15)N order parameters but not from the (13)C order parameters. Internal correlation times at (13)C' sites are on the average an order of magnitude longer than those at (15)N sites for the well-structured C-terminal subdomains, while the more flexible N-terminal subdomains have more comparable average internal correlation times.
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Affiliation(s)
- Liliya Vugmeyster
- Department of Chemistry and Environment and Natural Resources Institute, University of Alaska at Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA.
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20
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Siciliano A, Turrini F, Bertoldi M, Matte A, Pantaleo A, Olivieri O, De Franceschi L. Deoxygenation affects tyrosine phosphoproteome of red cell membrane from patients with sickle cell disease. Blood Cells Mol Dis 2010; 44:233-42. [DOI: 10.1016/j.bcmd.2010.02.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Accepted: 01/19/2010] [Indexed: 10/19/2022]
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21
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Chen L, Jiang ZG, Khan AA, Chishti AH, McKnight CJ. Dematin exhibits a natively unfolded core domain and an independently folded headpiece domain. Protein Sci 2009; 18:629-36. [PMID: 19241372 DOI: 10.1002/pro.59] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Dematin is an actin-binding protein originally identified in the junctional complex of the erythrocyte plasma membrane, and is present in many nonerythroid cells. Dematin headpiece knockout mice display a spherical red cell phenotype and develop a compensated anemia. Dematin has two domains: a 315-residue, proline-rich "core" domain and a 68-residue carboxyl-terminal villin-type "headpiece" domain. Expression of full-length dematin in E. coli as a GST recombinant protein results in truncation within a proline, glutamic acid, serine, threonine rich region (PEST). Therefore, we designed a mutant construct that replaces the PEST sequence. The modified dematin has high actin binding activity as determined by actin sedimentation assays. Negative stain electron microscopy demonstrates that the modified dematin also exhibits actin bundling activity like that of native dematin. Circular dichroism (CD) and NMR spectral analysis, however, show little secondary structure in the modified dematin. The lack of secondary structure is also observed in native dematin purified from human red blood cells. (15)N-HSQC NMR spectra of modified dematin indicate that the headpiece domain is fully folded whereas the core region is primarily unfolded. Our finding suggests that the core is natively unfolded and may serve as a scaffold to organize the components of the junctional complex.
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Affiliation(s)
- Lin Chen
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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22
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Brown JW, Vardar-Ulu D, McKnight CJ. How to arm a supervillin: designing F-actin binding activity into supervillin headpiece. J Mol Biol 2009; 393:608-18. [PMID: 19683541 DOI: 10.1016/j.jmb.2009.08.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 07/30/2009] [Accepted: 08/10/2009] [Indexed: 11/16/2022]
Abstract
Villin-type headpiece domains are compact motifs that have been used extensively as model systems for protein folding. Although the majority of headpiece domains bind actin, there are some that lack this activity. Here, we present the first NMR solution structure and (15)N-relaxation analysis of a villin-type headpiece domain natively devoid of F-actin binding activity, that of supervillin headpiece (SVHP). The structure was found to be similar to that of other headpiece domains that bind F-actin. Our NMR analysis demonstrates that SVHP lacks a conformationally flexible region (V-loop) present in all other villin-type headpiece domains and which is essential to the phosphoryl regulation of dematin headpiece. In comparing the electrostatic surface potential map of SVHP to that of other villin-type headpiece domains with significant affinity for F-actin, we identified a positive surface potential conserved among headpiece domains that bind F-actin but absent from SVHP. A single point mutation (L38K) in SVHP, which creates a similar positive surface potential, endowed SVHP with specific affinity for F-actin that is within an order of magnitude of the tightest binding headpiece domains. We propose that this effect is likely conferred by a specific buried salt bridge between headpiece and actin. As no high-resolution structural information exists for the villin-type headpiece F-actin complex, our results demonstrate that through positive mutagenesis, it is possible to design binding activity into homologous proteins without structural information of the counterpart's binding surface.
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Affiliation(s)
- Jeffrey W Brown
- Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA
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Mohseni M, Chishti AH. Regulatory models of RhoA suppression by dematin, a cytoskeletal adaptor protein. Cell Adh Migr 2009; 3:191-4. [PMID: 19262171 DOI: 10.4161/cam.3.2.7375] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Cell motility, adhesion and actin cytoskeletal rearrangements occur upon integrin-engagement to the extracellular matrix and activation of the small family of Rho GTPases, RhoA, Rac1 and Cdc42. The activity of the GTPases is regulated through associations with guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs) and guanine dissociation inhibitors (GDIs). Recent studies have demonstrated a critical role for actin-binding proteins, such as ezrin, radixin and moesin (ERM), in modulating the activity of small GTPases through their direct associations with GEFs, GAPs and GDI's. Dematin, an actin binding and bundling phospho-protein was first identified and characterized from the erythrocyte membrane, and has recently been implicated in regulating cell motility, adhesion and morphology by suppressing RhoA activation in mouse embryonic fibroblasts. Although the precise mechanism of RhoA suppression by dematin is unclear, several plausible and hypothetical models can be invoked. Dematin may bind and inhibit GEF activity, form an inactive complex with GDI-RhoA-GDP, or enhance GAP function. Dematin is the first actin-binding protein identified from the erythrocyte membrane that participates in GTPase signaling, and its broad expression suggests a conserved function in multiple tissues.
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Affiliation(s)
- Morvarid Mohseni
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, USA.
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Vugmeyster L, McKnight CJ. Phosphorylation-induced changes in backbone dynamics of the dematin headpiece C-terminal domain. JOURNAL OF BIOMOLECULAR NMR 2009; 43:39-50. [PMID: 19030997 PMCID: PMC2796552 DOI: 10.1007/s10858-008-9289-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Accepted: 10/20/2008] [Indexed: 05/27/2023]
Abstract
Dematin is an actin-binding protein abundant in red blood cells and other tissues. It contains a villin-type 'headpiece' F-actin-binding domain at its extreme C-terminus. The isolated dematin headpiece domain (DHP) undergoes a significant conformational change upon phosphorylation. The mutation of Ser74 to Glu closely mimics the phosphorylation of DHP. We investigated motions in the backbone of DHP and its mutant DHPS74E using several complementary NMR relaxation techniques: laboratory frame (15)N NMR relaxation, which is sensitive primarily to the ps-ns time scale, cross-correlated chemical shift modulation NMR relaxation detecting correlated mus-ms time scale motions of neighboring (13)C' and (15)N nuclei, and cross-correlated relaxation of two (15)N-(1)H dipole-dipole interactions detecting slow motions of backbone NH vectors in successive amino acid residues. The results indicate a reduction in mobility upon the mutation in several regions of the protein. The additional salt bridge formed in DHPS74E that links the N- and C-terminal subdomains is likely to be responsible for these changes.
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Affiliation(s)
- Liliya Vugmeyster
- Department of Chemistry, University of Alaska at Anchorage, 99508, USA.
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25
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Moaddel R, Wainer IW. Conformational mobility of immobilized proteins. J Pharm Biomed Anal 2006; 43:399-406. [PMID: 17095178 DOI: 10.1016/j.jpba.2006.08.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2006] [Accepted: 08/20/2006] [Indexed: 11/15/2022]
Abstract
Cellular membrane fragments have been immobilized on the surface of a silica-based liquid chromatographic support and on the surface of glass capillaries to create immobilized receptor and drug transporter columns. These columns have included phases containing one subtype of the nicotinic receptor (alpha3beta2, alpha3beta4, alpha4beta2, alpha4beta4) and the P-glycoprotein transporter. A key question in the application of these columns to drug discovery and development is the ability of the immobilized receptor or transporter to undergo ligand and/or co-factor induced conformational changes. Using frontal affinity chromatographic techniques and non-linear chromatographic techniques it has been demonstrated that the immobilized nicotinic receptors undergo agonist-induced conformational shifts from the resting to desensitized states with corresponding changes in binding affinities and enantioselectivities. Ligand-induced allosteric interactions and ATP-driven conformational changes have also been demonstrated with the immobilized Pgp stationary phase. The results demonstrate that the immobilized proteins retained their ability to undergo conformational mobility and that this is an attractive alternative to allow for the full characterization of multiple protein conformations.
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Affiliation(s)
- Ruin Moaddel
- Gerontology Research Center, National Institutes in Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224-6825, USA.
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