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Samba-Louaka A, Delafont V, Rodier MH, Cateau E, Héchard Y. Free-living amoebae and squatters in the wild: ecological and molecular features. FEMS Microbiol Rev 2019; 43:415-434. [DOI: 10.1093/femsre/fuz011] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 04/30/2019] [Indexed: 02/06/2023] Open
Abstract
ABSTRACT
Free-living amoebae are protists frequently found in water and soils. They feed on other microorganisms, mainly bacteria, and digest them through phagocytosis. It is accepted that these amoebae play an important role in the microbial ecology of these environments. There is a renewed interest for the free-living amoebae since the discovery of pathogenic bacteria that can resist phagocytosis and of giant viruses, underlying that amoebae might play a role in the evolution of other microorganisms, including several human pathogens. Recent advances, using molecular methods, allow to bring together new information about free-living amoebae. This review aims to provide a comprehensive overview of the newly gathered insights into (1) the free-living amoeba diversity, assessed with molecular tools, (2) the gene functions described to decipher the biology of the amoebae and (3) their interactions with other microorganisms in the environment.
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Affiliation(s)
- Ascel Samba-Louaka
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
| | - Vincent Delafont
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
| | - Marie-Hélène Rodier
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
- Laboratoire de Parasitologie et Mycologie, CHU La Milétrie, 2 rue de la Milétrie, 86021 Poitiers Cedex, France
| | - Estelle Cateau
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
- Laboratoire de Parasitologie et Mycologie, CHU La Milétrie, 2 rue de la Milétrie, 86021 Poitiers Cedex, France
| | - Yann Héchard
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
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Schroeter MM, Orlova A, Egelman EH, Beall B, Chalovich JM. Organization of F-actin by Fesselin (avian smooth muscle synaptopodin 2). Biochemistry 2013; 52:4955-61. [PMID: 23789719 PMCID: PMC3842371 DOI: 10.1021/bi4005254] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Fesselin or avian synaptopodin 2 is a member of the synaptopodin family of actin binding proteins. Fesselin promotes G-actin polymerization and the formation of large actin complexes that can be collected by low-speed centrifugation. Because of the potential role of fesselin in some cancers and its effects on actin, we further investigated the effect of fesselin on actin. Fesselin initiated actin polymerization under a variety of conditions, including the virtual absence of salt. Actin filaments formed at low salt concentrations in the presence of fesselin were similar to filaments polymerized in the presence of 100 mM KCl. In both cases, the filaments were long and straight with a common orientation. Highly ordered actin bundles formed with increasing times of incubation. Blockers of actin growth at the barbed end (cytochalasin D and CapZ) did not prevent fesselin from polymerizing actin. Low concentrations of fesselin increased the critical concentration of actin. Both observations are consistent with preferential growth at the pointed end of actin filaments. These results indicate a role of fesselin in organizing cellular actin. These and other results indicate that fesselin is part of a cellular actin organizing center.
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Affiliation(s)
- Mechthild M. Schroeter
- Institute of Vegetative Physiology University of Cologne, Robert Koch Strasse 39, D-50931 Cologne, Germany Phone: +49-221-478-7855 Fax: +49-221-478-3538
| | - Albina Orlova
- Department of Biochemistry and Molecular Genetics University of Virginia Box 800733 Charlottesville, VA 22908-0733 Phone: 434-924-8210 Fax: 434-924-5069
| | - Edward H. Egelman
- Department of Biochemistry and Molecular Genetics University of Virginia Box 800733 Charlottesville, VA 22908-0733 Phone: 434-924-8210 Fax: 434-924-5069
| | - Brent Beall
- Department of Biotechnology Athens Technical College 800 US HWY 29N Athens, GA 30601 Phone: 706-227-5350 Fax: 706-425-3104
| | - Joseph M. Chalovich
- Department of Biochemistry & Molecular Biology Brody School of Medicine at East Carolina University 600 Moye Blvd. Greenville, NC 27834-4300, USA Phone: 252-744-2973
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Mahaffy RE, Pollard TD. Kinetics of the formation and dissociation of actin filament branches mediated by Arp2/3 complex. Biophys J 2006; 91:3519-28. [PMID: 16905606 PMCID: PMC1614474 DOI: 10.1529/biophysj.106.080937] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The actin filament network at the leading edge of motile cells relies on localized branching by Arp2/3 complex from "mother" filaments growing near the plasma membrane. The nucleotide bound to the mother filaments (ATP, ADP and phosphate, or ADP) may influence the branch dynamics. To determine the effect of the nucleotide bound to the subunits of the mother filament on the formation and stability of branches, we compared the time courses of actin polymerization in bulk samples measured using the fluorescence of pyrene actin with observations of single filaments by total internal reflection fluorescence microscopy. Although the branch nucleation rate in bulk samples was nearly the same regardless of the nucleotide on the mother filaments, we observed fewer branches by microscopy on ADP-bound filaments than on ADP-P(i)-bound filaments. Observation of branches in the microscope depends on their binding to the slide. Since the probability that a branch binds to the slide is directly related to its lifetime, we used counts of branches to infer their rates of dissociation from mother filaments. We conclude that the nucleotide on the mother filament does not affect the initial branching event but that branches are an order of magnitude more stable on the sides of new ATP- or ADP-P(i) filaments than on ADP-actin filaments.
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Affiliation(s)
- Rachel E Mahaffy
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
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Pollard TD, Blanchoin L, Mullins RD. Molecular mechanisms controlling actin filament dynamics in nonmuscle cells. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2001; 29:545-76. [PMID: 10940259 DOI: 10.1146/annurev.biophys.29.1.545] [Citation(s) in RCA: 1069] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We review how motile cells regulate actin filament assembly at their leading edge. Activation of cell surface receptors generates signals (including activated Rho family GTPases) that converge on integrating proteins of the WASp family (WASp, N-WASP, and Scar/WAVE). WASP family proteins stimulate Arp2/3 complex to nucleate actin filaments, which grow at a fixed 70 degrees angle from the side of pre-existing actin filaments. These filaments push the membrane forward as they grow at their barbed ends. Arp2/3 complex is incorporated into the network, and new filaments are capped rapidly, so that activated Arp2/3 complex must be supplied continuously to keep the network growing. Hydrolysis of ATP bound to polymerized actin followed by phosphate dissociation marks older filaments for depolymerization by ADF/cofilins. Profilin catalyzes exchange of ADP for ATP, recycling actin back to a pool of unpolymerized monomers bound to profilin and thymosin-beta 4 that is poised for rapid elongation of new barbed ends.
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Affiliation(s)
- T D Pollard
- Structural Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA.
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Taylor KA, Taylor DW, Schachat F. Isoforms of alpha-actinin from cardiac, smooth, and skeletal muscle form polar arrays of actin filaments. J Cell Biol 2000; 149:635-46. [PMID: 10791977 PMCID: PMC2174853 DOI: 10.1083/jcb.149.3.635] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We have used a positively charged lipid monolayer to form two-dimensional bundles of F-actin cross-linked by alpha-actinin to investigate the relative orientation of the actin filaments within them. This method prevents growth of the bundles perpendicular to the monolayer plane, thereby facilitating interpretation of the electron micrographs. Using alpha-actinin isoforms isolated from the three types of vertebrate muscle, i.e., cardiac, skeletal, and smooth, we have observed almost exclusively cross-linking between polar arrays of filaments, i.e., actin filaments with their plus ends oriented in the same direction. One type of bundle can be classified as an Archimedian spiral consisting of a single actin filament that spirals inward as the filament grows and the bundle is formed. These spirals have a consistent hand and grow to a limiting internal diameter of 0.4-0.7 microm, where the filaments appear to break and spiral formation ceases. These results, using isoforms usually characterized as cross-linkers of bipolar actin filament bundles, suggest that alpha-actinin is capable of cross-linking actin filaments in any orientation. Formation of specifically bipolar or polar filament arrays cross-linked by alpha-actinin may require additional factors that either determine the filament orientation or restrict the cross-linking capabilities of alpha-actinin.
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Affiliation(s)
- K A Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-3015, USA.
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Kelleher JF, Mullins RD, Pollard TD. Purification and assay of the Arp2/3 complex from Acanthamoeba castellanii. Methods Enzymol 1998; 298:42-51. [PMID: 9751870 DOI: 10.1016/s0076-6879(98)98007-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- J F Kelleher
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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Mullins RD, Kelleher JF, Xu J, Pollard TD. Arp2/3 complex from Acanthamoeba binds profilin and cross-links actin filaments. Mol Biol Cell 1998; 9:841-52. [PMID: 9529382 PMCID: PMC25311 DOI: 10.1091/mbc.9.4.841] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/1997] [Accepted: 01/20/1998] [Indexed: 02/07/2023] Open
Abstract
The Arp2/3 complex was first purified from Acanthamoeba castellanii by profilin affinity chromatography. The mechanism of interaction with profilin was unknown but was hypothesized to be mediated by either Arp2 or Arp3. Here we show that the Arp2 subunit of the complex can be chemically cross-linked to the actin-binding site of profilin. By analytical ultracentrifugation, rhodamine-labeled profilin binds Arp2/3 complex with a Kd of 7 microM, an affinity intermediate between the low affinity of profilin for barbed ends of actin filaments and its high affinity for actin monomers. These data suggest the barbed end of Arp2 is exposed, but Arp2 and Arp3 are not packed together in the complex exactly like two actin monomers in a filament. Arp2/3 complex also cross-links actin filaments into small bundles and isotropic networks, which are mechanically stiffer than solutions of actin filaments alone. Arp2/3 complex is concentrated at the leading edge of motile Acanthamoeba, and its localization is distinct from that of alpha-actinin, another filament cross-linking protein. Based on localization and actin filament nucleation and cross-linking activities, we propose a role for Arp2/3 in determining the structure of the actin filament network at the leading edge of motile cells.
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Affiliation(s)
- R D Mullins
- The Salk Institute for Biological Studies, La Jolla California 92037, USA
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Kelleher JF, Atkinson SJ, Pollard TD. Sequences, structural models, and cellular localization of the actin-related proteins Arp2 and Arp3 from Acanthamoeba. J Cell Biol 1995; 131:385-97. [PMID: 7593166 PMCID: PMC2199984 DOI: 10.1083/jcb.131.2.385] [Citation(s) in RCA: 154] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We cloned and sequenced the two actin-related proteins (Arps) present in the profilin-binding complex of Acanthamoeba (Machesky, L. M., S. J. Atkinson, C. Ampe, J. Vandekerckhove, and T. D. Pollard. 1994, J. Cell Biol. 127:107-115). The sequence of Arp2 is more similar to other Arp2s than to actin, while the sequence of Arp3 is more similar to other Arp3s than to actin. Phylogenetic analysis of all known Arps demonstrates that most group into three major families, which are likely to be shared across all eukaryotic phyla. Together with conventional actins, the Arps form a larger family distinct from structurally related ATPases such as Hsp70's and sugar kinases. Atomic models of the Arps based on their sequences and the structure of actin provide some clues about function. Both Arps have atoms appropriately placed to bind ATP and divalent cation. Arp2, but not Arp3, has a conserved profilin-binding site. Neither Arp has the residues required to copolymerize with actin, but an Arp heterodimer present in the profilin-binding complex might serve as a pointed end nucleus for actin polymerization. Both Acanthamoeba Arps are soluble in cell homogenates, and both are concentrated in the cortex of Acanthamoeba. The cellular concentrations are 1.9 microM Arp2 and 5.1 microM Arp3, substoichiometric to actin (200 microM) but comparable to many actin-binding proteins.
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Affiliation(s)
- J F Kelleher
- Department of Cell Biology and Anatomy, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA
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Kuroda M, Kohira Y, Sasaki M. Conformational change of skeletal muscle alpha-actinin induced by salt. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1205:97-104. [PMID: 8142490 DOI: 10.1016/0167-4838(94)90097-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We examined the effect of KCl concentration on conformation of skeletal muscle alpha-actinin. One-dimensional peptide maps of alpha-actinin digested with chymotrypsin indicated that alpha-actinin can take on at least three different conformations depending on the KCl concentration of the solvent, i.e., at low (0-0.02 M KCl), intermediate (0.05-0.2 M KCl), and high (0.3-0.6 M KCl) salt concentration. Viscosity measurement and gel-filtration chromatography of alpha-actinin at these three salt ranges indicated that the axial ratio of alpha-actinin increased as the ionic strength of the solvent decreased. By assuming 45% hydration of the alpha-actinin molecule and using a molecular weight of 210,000, dimensions of alpha-actinin were calculated from viscosity data. The size estimated under the low-salt conditions was 3.2 x 74.2 nm. They were 3.4 x 51.3 nm and 4.5 x 40.1 nm, respectively, in the intermediate and high salt ranges. The result of the gel-filtration chromatography showed that the conformational change was reversible and that the change took place through the elongation and/or shortening of the rod domain of the molecule. We explain the salt-induced length change of alpha-actinin by the twisted-coiling model proposed by McGough and Josephs for erythrocyte spectrin (McGough, A. and Josephs, R. (1990) Proc. Natl. Acad. Sci. USA 87, 5208-5212). Pelleting experiments indicated that the conformational change affected the binding ratio between alpha-actinin and actin.
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Affiliation(s)
- M Kuroda
- Department of Biology, Faculty of Science, Shimane University, Japan
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Wachsstock DH, Schwartz WH, Pollard TD. Affinity of alpha-actinin for actin determines the structure and mechanical properties of actin filament gels. Biophys J 1993; 65:205-14. [PMID: 8369430 PMCID: PMC1225716 DOI: 10.1016/s0006-3495(93)81059-2] [Citation(s) in RCA: 178] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Proteins that cross-link actin filaments can either form bundles of parallel filaments or isotropic networks of individual filaments. We have found that mixtures of actin filaments with alpha-actinin purified from either Acanthamoeba castellanii or chicken smooth muscle can form bundles or isotropic networks depending on their concentration. Low concentrations of alpha-actinin and actin filaments form networks indistinguishable in electron micrographs from gels of actin alone. Higher concentrations of alpha-actinin and actin filaments form bundles. The threshold for bundling depends on the affinity of the alpha-actinin for actin. The complex of Acanthamoeba alpha-actinin with actin filaments has a Kd of 4.7 microM and a bundling threshold of 0.1 microM; chicken smooth muscle has a Kd of 0.6 microM and a bundling threshold of 1 microM. The physical properties of isotropic networks of cross-linked actin filaments are very different from a gel of bundles: the network behaves like a solid because each actin filament is part of a single structure that encompasses all the filaments. Bundles of filaments behave more like a very viscous fluid because each bundle, while very long and stiff, can slip past other bundles. We have developed a computer model that predicts the bundling threshold based on four variables: the length of the actin filaments, the affinity of the alpha-actinin for actin, and the concentrations of actin and alpha-actinin.
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Affiliation(s)
- D H Wachsstock
- Department of Cell Biology and Anatomy, Johns Hopkins University, Baltimore, Maryland 21205
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Meyer RK, Aebi U. Bundling of actin filaments by alpha-actinin depends on its molecular length. J Biophys Biochem Cytol 1990; 110:2013-24. [PMID: 2351691 PMCID: PMC2116144 DOI: 10.1083/jcb.110.6.2013] [Citation(s) in RCA: 226] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cross-linking of actin filaments (F-actin) into bundles and networks was investigated with three different isoforms of the dumbbell-shaped alpha-actinin homodimer under identical reaction conditions. These were isolated from chicken gizzard smooth muscle, Acanthamoeba, and Dictyostelium, respectively. Examination in the electron microscope revealed that each isoform was able to cross-link F-actin into networks. In addition, F-actin bundles were obtained with chicken gizzard and Acanthamoeba alpha-actinin, but not Dictyostelium alpha-actinin under conditions where actin by itself polymerized into disperse filaments. This F-actin bundle formation critically depended on the proper molar ratio of alpha-actinin to actin, and hence F-actin bundles immediately disappeared when free alpha-actinin was withdrawn from the surrounding medium. The apparent dissociation constants (Kds) at half-saturation of the actin binding sites were 0.4 microM at 22 degrees C and 1.2 microM at 37 degrees C for chicken gizzard, and 2.7 microM at 22 degrees C for both Acanthamoeba and Dictyostelium alpha-actinin. Chicken gizzard and Dictyostelium alpha-actinin predominantly cross-linked actin filaments in an antiparallel fashion, whereas Acanthamoeba alpha-actinin cross-linked actin filaments preferentially in a parallel fashion. The average molecular length of free alpha-actinin was 37 nm for glycerol-sprayed/rotary metal-shadowed and 35 nm for negatively stained chicken gizzard; 46 and 44 nm, respectively, for Acanthamoeba; and 34 and 31 nm, respectively, for Dictyostelium alpha-actinin. In negatively stained preparations we also evaluated the average molecular length of alpha-actinin when bound to actin filaments: 36 nm for chicken gizzard and 35 nm for Acanthamoeba alpha-actinin, a molecular length roughly coinciding with the crossover repeat of the two-stranded F-actin helix (i.e., 36 nm), but only 28 nm for Dictyostelium alpha-actinin. Furthermore, the minimal spacing between cross-linking alpha-actinin molecules along actin filaments was close to 36 nm for both smooth muscle and Acanthamoeba alpha-actinin, but only 31 nm for Dictyostelium alpha-actinin. This observation suggests that the molecular length of the alpha-actinin homodimer may determine its spacing along the actin filament, and hence F-actin bundle formation may require "tight" (i.e., one molecule after the other) and "untwisted" (i.e., the long axis of the molecule being parallel to the actin filament axis) packing of alpha-actinin molecules along the actin filaments.
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Affiliation(s)
- R K Meyer
- M. E. Müller-Institute for High Resolution Electron Microscopy Biocenter, University of Basel, Switzerland
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Miller KG, Field CM, Alberts BM. Actin-binding proteins from Drosophila embryos: a complex network of interacting proteins detected by F-actin affinity chromatography. J Cell Biol 1989; 109:2963-75. [PMID: 2512303 PMCID: PMC2115944 DOI: 10.1083/jcb.109.6.2963] [Citation(s) in RCA: 132] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
By using F-actin affinity chromatography columns to select proteins solely by their ability to bind to actin filaments, we have identified and partially purified greater than 40 proteins from early Drosophila embryos. These proteins represent approximately 0.5% of the total protein present in soluble cell extracts, and 2 mg are obtained by chromatography of an extract from 10 g of embryos. As judged by immunofluorescence of fixed embryos, 90% of the proteins that we have detected in F-actin column eluates are actin-associated in vivo (12 of 13 proteins tested). The distributions of antigens observed suggest that groups of these proteins cooperate in generating unique actin structures at different places in the cell. These structures change as cells progress through the cell cycle and as they undergo the specializations that accompany development. The variety of different spatial localizations that we have observed in a small subset of the total actin-binding proteins suggests that the actin cytoskeleton is a very complex network of interacting proteins.
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Affiliation(s)
- K G Miller
- Department of Biochemistry and Biophysics, University of California, San Francisco 94143
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Hoffman EP, Watkins SC, Slayter HS, Kunkel LM. Detection of a specific isoform of alpha-actinin with antisera directed against dystrophin. J Cell Biol 1989; 108:503-10. [PMID: 2645301 PMCID: PMC2115443 DOI: 10.1083/jcb.108.2.503] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We have characterized a protein immunologically related to dystrophin, the protein product of the Duchenne muscular dystrophy gene. We identify this related protein as a fast-twitch glycolytic isoform (mouse extensor digitorum longus-specific) of myofibrillar alpha-actinin. This specific isoform of alpha-actinin exhibits a more restricted pattern of expression in skeletal muscle than fast-twitch-specific isoforms of both myosin and Ca2+-ATPase. Our results provide evidence that dystrophin and myofibrillar alpha-actinin are related proteins, reinforcing the previous data concerning the sequence homologies noted between nonmuscle cytoskeletal alpha-actinin and dystrophin. In addition, we describe the first antisera directed against a specific myofibrillar skeletal muscle isoform of alpha-actinin.
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Affiliation(s)
- E P Hoffman
- Division of Genetics, Children's Hospital, Boston, Massachusetts 02115
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Kaiser DA, Goldschmidt-Clermont PJ, Levine BA, Pollard TD. Characterization of renatured profilin purified by urea elution from poly-L-proline agarose columns. CELL MOTILITY AND THE CYTOSKELETON 1989; 14:251-62. [PMID: 2611892 DOI: 10.1002/cm.970140211] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We present evidence that native profilin can be purified from cellular extracts of Acanthamoeba, Dictyostelium, and human platelets by affinity chromatography on poly-L-proline agarose. After applying cell extracts and washing the column with 3 M urea, homogeneous profilin is eluted by increasing the urea concentration to 6-8 M. Acanthamoeba profilin-I and profilin-II can subsequently be separated by cation exchange chromatography. The yield of Acanthamoeba profilin is twice that obtained by conventional methods. Several lines of evidence show that the profilins fully renature after removal of the urea by dialysis: 1) dialyzed Acanthamoeba and human profilins rebind quantitatively to poly-L-proline and bind to actin in the same way as native, conventionally purified profilin without urea treatment; 2) dialyzed profilins form 3-D crystals under the same conditions as native profilins; 3) dialyzed Acanthamoeba profilin-I has an NMR spectrum identical with that of native profilin-I; and 4) dialyzed human and Acanthamoeba profilins inhibit actin polymerization. We report the discovery of profilin in Dictyostelium cell extracts using the same method. Based on these observations we conclude that urea elution from poly-L-proline agarose followed by renaturation will be generally useful for preparing profilins from a wide variety of cells. Perhaps also of general use is the finding that either myosin-II or alpha-actinin in crude cell extracts can be bound selectively to the poly-L-proline agarose column depending on the ionic conditions used to equilibrate the column. We have purified myosin-II from both Acanthamoeba and Dictyostelium cell extracts and alpha-actinin from Acanthamoeba cell extracts in the appropriate buffers. These proteins are retained as complexes with actin by the agarose and not by a specific interaction with poly-L-proline. They can be eluted by dissociating the complexes with ATP and separated from actin by gel filtration if necessary.
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Affiliation(s)
- D A Kaiser
- Department of Cell Biology and Anatomy, Johns Hopkins Medical School, Baltimore, MD 21205
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