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Lu L, Li J, Moussaoui M, Boix E. Immune Modulation by Human Secreted RNases at the Extracellular Space. Front Immunol 2018; 9:1012. [PMID: 29867984 PMCID: PMC5964141 DOI: 10.3389/fimmu.2018.01012] [Citation(s) in RCA: 102] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 04/23/2018] [Indexed: 12/23/2022] Open
Abstract
The ribonuclease A superfamily is a vertebrate-specific family of proteins that encompasses eight functional members in humans. The proteins are secreted by diverse innate immune cells, from blood cells to epithelial cells and their levels in our body fluids correlate with infection and inflammation processes. Recent studies ascribe a prominent role to secretory RNases in the extracellular space. Extracellular RNases endowed with immuno-modulatory and antimicrobial properties can participate in a wide variety of host defense tasks, from performing cellular housekeeping to maintaining body fluid sterility. Their expression and secretion are induced in response to a variety of injury stimuli. The secreted proteins can target damaged cells and facilitate their removal from the focus of infection or inflammation. Following tissue damage, RNases can participate in clearing RNA from cellular debris or work as signaling molecules to regulate the host response and contribute to tissue remodeling and repair. We provide here an overall perspective on the current knowledge of human RNases’ biological properties and their role in health and disease. The review also includes a brief description of other vertebrate family members and unrelated extracellular RNases that share common mechanisms of action. A better knowledge of RNase mechanism of actions and an understanding of their physiological roles should facilitate the development of novel therapeutics.
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Affiliation(s)
- Lu Lu
- Department of Biochemistry and Molecular Biology, Faculty of Biosciences, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
| | - Jiarui Li
- Department of Biochemistry and Molecular Biology, Faculty of Biosciences, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
| | - Mohammed Moussaoui
- Department of Biochemistry and Molecular Biology, Faculty of Biosciences, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
| | - Ester Boix
- Department of Biochemistry and Molecular Biology, Faculty of Biosciences, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
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2
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Dey S, Levy ED. Inferring and Using Protein Quaternary Structure Information from Crystallographic Data. Methods Mol Biol 2018; 1764:357-375. [PMID: 29605927 DOI: 10.1007/978-1-4939-7759-8_23] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A precise knowledge of the quaternary structure of proteins is essential to illuminate both their function and their evolution. The major part of our knowledge on quaternary structure is inferred from X-ray crystallography data, but this inference process is hard and error-prone. The difficulty lies in discriminating fortuitous protein contacts, which make up the lattice of protein crystals, from biological protein contacts that exist in the native cellular environment. Here, we review methods devised to discriminate between both types of contacts and describe resources for downloading protein quaternary structure information and identifying high-confidence quaternary structures. The use of high-confidence datasets of quaternary structures will be critical for the analysis of structural, functional, and evolutionary properties of proteins.
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Affiliation(s)
- Sucharita Dey
- Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Emmanuel D Levy
- Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel.
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3
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Gupta SK, Haigh BJ, Griffin FJ, Wheeler TT. The mammalian secreted RNases: Mechanisms of action in host defence. Innate Immun 2012; 19:86-97. [DOI: 10.1177/1753425912446955] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The mammalian ribonucleaseA family comprises a large group of structurally similar proteins which are secreted by a range of tissues and immune cells. Their physiological role is unclear. It has been suggested that some of these RNases contribute to host defence, notably eosinophil-derived neurotoxin, eosinophil cationic protein, eosinophil-associated RNases, RNase4, angiogenin (RNase5), RNase7, RNase8 and bovine seminal RNase. This review summarises data supporting the involvement of these proteins in host defence, focusing on their antimicrobial, cytotoxic and immunomodulatory activities. The extent to which the data support possible mechanisms of action for these proteins is discussed. This compilation of findings and current hypotheses on the physiological role of these RNases will provide a stimulus for further research and development of ideas on the contribution of the RNases to host defence.
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Affiliation(s)
- Sandeep K Gupta
- AgResearch Ltd, Ruakura Research Centre, Hamilton, New Zealand
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Brendan J Haigh
- AgResearch Ltd, Ruakura Research Centre, Hamilton, New Zealand
| | - Frank J Griffin
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
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4
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Spadaccini R, Ercole C, Gentile MA, Sanfelice D, Boelens R, Wechselberger R, Batta G, Bernini A, Niccolai N, Picone D. NMR studies on structure and dynamics of the monomeric derivative of BS-RNase: new insights for 3D domain swapping. PLoS One 2012; 7:e29076. [PMID: 22253705 PMCID: PMC3257227 DOI: 10.1371/journal.pone.0029076] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 11/20/2011] [Indexed: 11/18/2022] Open
Abstract
Three-dimensional domain swapping is a common phenomenon in pancreatic-like ribonucleases. In the aggregated state, these proteins acquire new biological functions, including selective cytotoxicity against tumour cells. RNase A is able to dislocate both N- and C-termini, but usually this process requires denaturing conditions. In contrast, bovine seminal ribonuclease (BS-RNase), which is a homo-dimeric protein sharing 80% of sequence identity with RNase A, occurs natively as a mixture of swapped and unswapped isoforms. The presence of two disulfides bridging the subunits, indeed, ensures a dimeric structure also to the unswapped molecule. In vitro, the two BS-RNase isoforms interconvert under physiological conditions. Since the tendency to swap is often related to the instability of the monomeric proteins, in these paper we have analysed in detail the stability in solution of the monomeric derivative of BS-RNase (mBS) by a combination of NMR studies and Molecular Dynamics Simulations. The refinement of NMR structure and relaxation data indicate a close similarity with RNase A, without any evidence of aggregation or partial opening. The high compactness of mBS structure is confirmed also by H/D exchange, urea denaturation, and TEMPOL mapping of the protein surface. The present extensive structural and dynamic investigation of (monomeric) mBS did not show any experimental evidence that could explain the known differences in swapping between BS-RNase and RNase A. Hence, we conclude that the swapping in BS-RNase must be influenced by the distinct features of the dimers, suggesting a prominent role for the interchain disulfide bridges.
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Affiliation(s)
- Roberta Spadaccini
- Dipartimento di Scienze Biologiche ed Ambientali, Università del Sannio, Benevento, Italy
| | - Carmine Ercole
- Dipartimento di Chimica, Università degli Studi di Napoli “Federico II”, Napoli, Italy
| | - Maria A. Gentile
- Dipartimento di Chimica, Università degli Studi di Napoli “Federico II”, Napoli, Italy
| | - Domenico Sanfelice
- Dipartimento di Chimica, Università degli Studi di Napoli “Federico II”, Napoli, Italy
| | - Rolf Boelens
- Department of NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands
| | - Rainer Wechselberger
- Department of NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands
| | - Gyula Batta
- Institute of Chemistry, University of Debrecen, Debrecen, Hungary
| | - Andrea Bernini
- Dipartimento di Biotecnologie, Università degli Studi di Siena, Siena, Italy
| | - Neri Niccolai
- Dipartimento di Biotecnologie, Università degli Studi di Siena, Siena, Italy
| | - Delia Picone
- Dipartimento di Chimica, Università degli Studi di Napoli “Federico II”, Napoli, Italy
- * E-mail:
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5
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Yadid I, Tawfik DS. Functional β-propeller lectins by tandem duplications of repetitive units. Protein Eng Des Sel 2010; 24:185-95. [DOI: 10.1093/protein/gzq053] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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6
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Does domain swapping improve the stability of RNase A? Biochem Biophys Res Commun 2009; 382:114-8. [DOI: 10.1016/j.bbrc.2009.02.142] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Accepted: 02/26/2009] [Indexed: 11/21/2022]
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7
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Kazakou K, Holloway DE, Prior SH, Subramanian V, Acharya KR. Ribonuclease A homologues of the zebrafish: polymorphism, crystal structures of two representatives and their evolutionary implications. J Mol Biol 2008; 380:206-22. [PMID: 18508078 PMCID: PMC2582337 DOI: 10.1016/j.jmb.2008.04.070] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 04/24/2008] [Accepted: 04/27/2008] [Indexed: 12/21/2022]
Abstract
The widespread and functionally varied members of the ribonuclease A (RNase A) superfamily provide an excellent opportunity to study evolutionary forces at work on a conserved protein scaffold. Representatives from the zebrafish are of particular interest as the evolutionary distance from non-ichthyic homologues is large. We conducted an exhaustive survey of available zebrafish DNA sequences and found significant polymorphism among its four known homologues. In an extension of previous nomenclature, the variants have been named RNases ZF-1a–c,-2a–d,-3a–e and-4. We present the first X-ray crystal structures of zebrafish ribonucleases, RNases ZF-1a and-3e at 1.35-and 1.85 Å resolution, respectively. Structure-based clustering with ten other ribonuclease structures indicates greatest similarity to mammalian angiogenins and amphibian ribonucleases, and supports the view that all present-day ribonucleases evolved from a progenitor with three disulphide bonds. In their details, the two structures are intriguing melting-pots of features present in ribonucleases from other vertebrate classes. Whereas in RNase ZF-1a the active site is obstructed by the C-terminal segment (as observed in angiogenin), in RNase ZF-3e the same region is open (as observed in more catalytically efficient homologues). The progenitor of present-day ribonucleases is more likely to have had an obstructive C terminus, and the relatively high similarity (late divergence) of RNases ZF-1 and-3 infers that the active site unblocking event has happened independently in different vertebrate lineages.
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8
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Abstract
The Ribonuclease A superfamily includes an extensive network of distinct and divergent gene lineages. Although all ribonucleases of this superfamily share invariant structural and catalytic elements and some degree of enzymatic activity, the primary sequences have diverged significantly, ostensibly to promote novel function. We will review the literature on the evolution and biology of the RNase A ribonuclease lineages that have been characterized specifically as involved in host defense including: (1) RNases 2 and RNases 3, also known as the eosinophil ribonucleases, which are rapidly-evolving cationic proteins released from eosinophilic leukocytes, (2) RNase 7, an anti-pathogen ribonuclease identified in human skin, and (3) RNase 5, also known as angiogenin, another rapidly-evolving ribonuclease known to promote blood vessel growth with recently-discovered antibacterial activity. Interestingly, some of the characterized anti-pathogen activities do not depend on ribonuclease activity per se. We discuss the ways in which the anti-pathogen activities characterized in vitro might translate into experimental confirmation in vivo. We will also consider the possibility that other ribonucleases, such as the dimeric bovine seminal ribonuclease and the frog oocyte ribonucleases, may have host defense functions and therapeutic value that remain to be explored. (190 words).
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Affiliation(s)
- Kimberly D Dyer
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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9
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Levy Y, Cho SS, Onuchic JN, Wolynes PG. A Survey of Flexible Protein Binding Mechanisms and their Transition States Using Native Topology Based Energy Landscapes. J Mol Biol 2005; 346:1121-45. [PMID: 15701522 DOI: 10.1016/j.jmb.2004.12.021] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Revised: 12/03/2004] [Accepted: 12/09/2004] [Indexed: 11/16/2022]
Abstract
Many cellular functions rely on interactions between protein pairs and higher oligomers. We have recently shown that binding mechanisms are robust and owing to the minimal frustration principle, just as for protein folding, are governed primarily by the protein's native topology, which is characterized by the network of non-covalent residue-residue interactions. The detailed binding mechanisms of nine dimers, a trimer, and a tetramer, each involving different degrees of flexibility and plasticity during assembly, are surveyed here using a model that is based solely on the protein topology, having a perfectly funneled energy landscape. The importance of flexibility in binding reactions is manifested by the fly-casting effect, which is diminished in magnitude when protein flexibility is removed. Many of the grosser and finer structural aspects of the various binding mechanisms (including binding of pre-folded monomers, binding of intrinsically unfolded monomers, and binding by domain-swapping) predicted by the native topology based landscape model are consistent with the mechanisms found in the laboratory. An asymmetric binding mechanism is often observed for the formation of the symmetric homodimers where one monomer is more structured at the binding transition state and serves as a template for the folding of the other monomer. Phi values were calculated to show how the structure of the binding transition state ensemble would be manifested in protein engineering studies. For most systems, the simulated Phi values are reasonably correlated with the available experimental values. This agreement suggests that the overall binding mechanism and the nature of the binding transition state ensemble can be understood from the network of interactions that stabilize the native fold. The Phi values for the formation of an antibody-antigen complex indicate a possible role for solvation of the interface in biomolecular association of large rigid proteins.
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Affiliation(s)
- Yaakov Levy
- Center for Theoretical Biological Physics, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
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10
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Sica F, Di Fiore A, Merlino A, Mazzarella L. Structure and Stability of the Non-covalent Swapped Dimer of Bovine Seminal Ribonuclease. J Biol Chem 2004; 279:36753-60. [PMID: 15192098 DOI: 10.1074/jbc.m405655200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A growing number of pancreatic-type ribonucleases (RNases) present cytotoxic activity against malignant cells. The cytoxicity of these enzymes is related to their resistance to the ribonuclease protein inhibitor (RI). In particular, bovine seminal ribonuclease (BS-RNase) is toxic to tumor cells both in vitro and in vivo. BS-RNase is a covalent dimer with two intersubunit disulfide bridges between Cys(31) of one chain and Cys(32) of the second and vice versa. The native enzyme is an equilibrium mixture of two isomers, MxM and M=M. In the former the two subunits swap their N-terminal helices. The cytotoxic action is a peculiar property of MxM. In the reducing environment of cytosol, M=M dissociates into monomers, which are strongly inhibited by RI, whereas MxM remains as a non-covalent dimer (NCD), which evades RI. We have solved the crystal structure of NCD, carboxyamidomethylated at residues Cys(31) and Cys(32) (NCD-CAM), in a complex with 2'-deoxycitidylyl(3'-5')-2'-deoxyadenosine. The molecule reveals a quaternary structural organization much closer to MxM than to other N-terminal-swapped non-covalent dimeric forms of RNases. Model building of the complexes between these non-covalent dimers and RI reveals that NCD-CAM is the only dimer equipped with a quaternary organization capable of interfering seriously with the binding of the inhibitor. Moreover, a detailed comparative structural analysis of the dimers has highlighted the residues, which are mostly important in driving the quaternary structure toward that found in NCD-CAM.
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Affiliation(s)
- Filomena Sica
- Dipartimento di Chimica, Università degli Studi di Napoli Federico II, Via Cynthia, 80126 Naples, Italy
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11
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Jeong SY, Gaume B, Lee YJ, Hsu YT, Ryu SW, Yoon SH, Youle RJ. Bcl-x(L) sequesters its C-terminal membrane anchor in soluble, cytosolic homodimers. EMBO J 2004; 23:2146-55. [PMID: 15131699 PMCID: PMC424420 DOI: 10.1038/sj.emboj.7600225] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Accepted: 04/06/2004] [Indexed: 11/09/2022] Open
Abstract
Bcl-x(L) is a potent inhibitor of apoptosis. While Bcl-x(L) can be bound to mitochondria, a substantial fraction, depending on the cell type or tissue, is found in the cytosol of healthy cells. Gel filtration and crosslinking experiments reveal that, unlike monomeric Bax, Bcl-x(L) migrates in a complex of approximately 50 kDa in the cytosol. Co-immunoprecipitation experiments indicate that Bcl-x(L) in the cytosol forms homodimers. The C-terminal hydrophobic tails of two Bcl-x(L) molecules are involved in homodimer formation, and analysis of mutants demonstrates that the C-terminal lysine residue and the G138 residue lining the BH3-binding pocket are required for homodimerization. The flexible loop preceding the C-terminal tail in Bcl-x(L) is longer than that of several monomeric Bcl-2 family members and is a requisite for the homodimer formation. Bad binding to Bcl-x(L) dissociates the homodimers and triggers Bcl-x(L) binding to mitochondrial membranes. The C-terminal tail of Bcl-x(L) is also required to mediate Bcl-x(L)/Bax heterodimer formation. Both mitochondrial import and antiapoptotic activity of different Bcl-x(L) mutants correlate with their ability to form homodimers.
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Affiliation(s)
- Seon-Yong Jeong
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Brigitte Gaume
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Yang-Ja Lee
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Yi-Te Hsu
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
| | - Seung-Wook Ryu
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Soo-Han Yoon
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Richard J Youle
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Building 10, Room 4N-258, MSC 1414, 10 Center Drive, Bethesda, MD 20892-1414, USA. Tel.: +1 301 496 6628; Fax: +1 301 402 0380; E-mail: ,
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12
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Langedijk JPM, van Veelen PA, Schaaper WMM, de Ru AH, Meloen RH, Hulst MM. A structural model of pestivirus E(rns) based on disulfide bond connectivity and homology modeling reveals an extremely rare vicinal disulfide. J Virol 2002; 76:10383-92. [PMID: 12239315 PMCID: PMC136578 DOI: 10.1128/jvi.76.20.10383-10392.2002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2002] [Accepted: 07/02/2002] [Indexed: 11/20/2022] Open
Abstract
E(rns) is a pestivirus envelope glycoprotein and is the only known viral surface protein with RNase activity. E(rns) is a disulfide-linked homodimer of 100 kDa; it is found on the surface of pestivirus-infected cells and is secreted into the medium. In this study, the disulfide arrangement of the nine cysteines present in the mature dimer was established by analysis of the proteolytically cleaved protein. Fragments were obtained after digestion with multiple proteolytic enzymes and subsequently analyzed by liquid chromatography-electrospray ionization mass spectrometry. The analysis demonstrates which cysteine is involved in dimerization and reveals an extremely rare vicinal disulfide bridge of unknown function. With the assistance of the disulfide arrangement, a three-dimensional model was built by homology modeling based on the alignment with members of the Rh/T2/S RNase family. Compared to these other RNase family members, E(rns) shows an N-terminal truncation, a large insertion of a cystine-rich region, and a C-terminal extension responsible for membrane translocation. The homology to mammalian RNase 6 supports a possible role of E(rns) in B-cell depletion.
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Affiliation(s)
- J P M Langedijk
- Pepscan Systems Inc., Edelhertweg 15, PO Box 2098, 8203 AB Lelystad, The Netherlands.
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13
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Canals A, Pous J, Guasch A, Benito A, Ribó M, Vilanova M, Coll M. The structure of an engineered domain-swapped ribonuclease dimer and its implications for the evolution of proteins toward oligomerization. Structure 2001; 9:967-76. [PMID: 11591351 DOI: 10.1016/s0969-2126(01)00659-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
BACKGROUND Domain swapping has been proposed as a mechanism that explains the evolution from monomeric to oligomeric proteins. Bovine and human pancreatic ribonucleases are monomers with no biological properties other than their RNA cleavage ability. In contrast, the closely related bovine seminal ribonuclease is a natural domain-swapped dimer that has special biological properties, such as cytotoxicity to tumour cells. Several recombinant ribonuclease variants are domain-swapped dimers, but a structure of this kind has not yet been reported for the human enzyme. RESULTS The crystal structure at 2 A resolution of an engineered ribonuclease variant called PM8 reveals a new kind of domain-swapped dimer, based on the change of N-terminal domains between the two subunits. The swapping is fastened at both hinge peptides by the newly introduced Gln101, involved in two intermolecular hydrogen bonds and in a stacking interaction between residues of different chains. Two antiparallel salt bridges and water-mediated hydrogen bonds complete a new interface between subunits, while the hinge loop becomes organized in a 3(10) helix structure. CONCLUSIONS Proteins capable of domain swapping may quickly evolve toward an oligomeric form. As shown in the present structure, a single residue substitution reinforces the quaternary structure by forming an open interface. An evolutionary advantage derived from the new oligomeric state will fix the mutation and favour others, leading to a more extended complementary dimerization surface, until domain swapping is no longer necessary for dimer formation. The newly engineered swapped dimer reported here follows this hypothetical pathway for the rapid evolution of proteins.
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Affiliation(s)
- A Canals
- Laboratori d'Enginyeria de Proteïnes, Facultat de Ciències, Universitat de Girona, Campus de Montilivi, Girona E-17071, Spain
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14
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Lam SK, Ng TB. Isolation of a novel thermolabile heterodimeric ribonuclease with antifungal and antiproliferative activities from roots of the sanchi ginseng Panax notoginseng. Biochem Biophys Res Commun 2001; 285:419-23. [PMID: 11444859 DOI: 10.1006/bbrc.2001.5193] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An isolation procedure, consisting of ion exchange chromatography on CM-Sepharose, affinity chromatography on Affi-gel blue gel, and fast protein liquid chromatography on Mono S, was utilized to purify a base-nonspecific, heterodimeric ribonuclease (RNase) with diverse activities from roots of the sanchi ginseng Panax notoginseng. The RNase is unique in that it consists of two different nonglycoprotein subunits with a molecular weight of 27 and 29 kDa, respectively. The latter subunit is characterized by an N-terminal sequence showing remarkable similarity to that of the bitter gourd RNase. The Panax notoginseng RNase demonstrates potent RNase and translation-inhibitory activities. In addition, it exhibits antiproliferative activity toward leukemia L1210 cells and antifungal activity against Physalospora piricola and Coprinus comatus. Its RNase activity is not heat-resistant, unlike most RNases which are thermostable.
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Affiliation(s)
- S K Lam
- Department of Biochemistry, Chinese University of Hong Kong, Shatin, Hong Kong, China.
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15
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Abstract
Dimeric proteins can arise by the swapping of structural domains between monomers. The prevalence of this occurrence is unknown. Ribonuclease A (RNase A) is assumed to be a monomer near physiological conditions. Here, this hypothesis is tested and found to be imprecise. The two histidine residues (His12 and His119) in the active site of RNase A arise from two domains (S-peptide and S-protein) of the protein. The H12A and H119A variants have 10(5)-fold less ribonucleolytic activity than does the wild-type enzyme. Incubating a 1:1 mixture of the H12A and H119A variants at pH 6.5 and 65 degrees C results in a 10(3)-fold increase in ribonucleolytic activity. A large quantity of active dimer can be produced by lyophilizing a 1:1 mixture of the H12A and H119A variants from acetic acid. At pH 6.5 and 65 degrees C, the ribonucleolytic activity of this dimer converges to that of the dimer formed by simply incubating the monomers, as expected for a monomer-dimer equilibrium. The equilibrium dissociation constant for the dimer is near 2 mM at both 65 and 37 degrees C. This value of Kd is only 20-fold greater than the concentration of RNase A in the cow pancreas, suggesting that RNase A dimers exist in vivo. The intrinsic ability of RNase A to form dimers under physiological conditions is consistent with a detailed model for the evolution of homodimeric proteins. Dimers of "monomeric" proteins could be more prevalent than is usually appreciated.
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Affiliation(s)
- C Park
- Department of Biochemistry, University of Wisconsin-Madison, 53706, USA
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16
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Piccoli R, De Lorenzo C, Dal Piaz F, Pucci P, D'Alessio G. Trypsin sheds light on the singular case of seminal RNase, a dimer with two quaternary conformations. J Biol Chem 2000; 275:8000-6. [PMID: 10713119 DOI: 10.1074/jbc.275.11.8000] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dimeric seminal RNase presents the singular case of a dimer with access at equilibrium to two conformations: one in which the subunits exchange, or swap, their NH(2)-terminal arms; the other with no exchange. Thus a continuous unfolding/refolding of structural elements into two alternative conformations takes place in the native protein at equilibrium. The phenomenon was investigated by kinetic and mass spectrometric analyses of the effects of trypsin on the native protein, on its isolated quaternary forms, as well as on a monomeric derivative of the protein and on homologous dimeric RNase A. The kinetics of tryptic action on the protein forms and on the protein derivatives, as well as the location of the tryptic cleavage sites, and their chronological sequence, led to the identification of relevant interconversion intermediates, to the description of a model for the interconversion process, and to a hypothesis for the unique phenomenon of the dual quaternary conformation of seminal RNase.
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Affiliation(s)
- R Piccoli
- Dipartimento di Chimica Organica e Biologica, Università di Napoli Federico II, Via Mezzocannone 16, 80134 Naples, Italy
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