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Choo M, Oh S, Jo S, Jin X, Song Y, Wen H, Park S, Kang S. Highly conserved protein Rv1211 in Mycobacterium tuberculosis is a natively unfolded protein that binds to a calmodulin antagonist, trifluoperazine. Biochem Biophys Res Commun 2022; 610:182-187. [PMID: 35468422 DOI: 10.1016/j.bbrc.2022.04.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 04/10/2022] [Indexed: 11/02/2022]
Abstract
Rv1211 is a conserved hypothetical protein in Mycobacterium tuberculosis and is required for the growth and pathogenesis of the bacteria. The protein has been suggested as a calmodulin-like calcium-binding protein with an EF-hand motif and as a target of trifluoperazine, a calmodulin antagonist in eukaryotes that inhibits mycobacterial growth. Here, we expressed the recombinant protein of Rv1211 and performed structural and biochemical studies of Rv1211 and its interaction with Ca2+ or trifluoperazine. Surprisingly, Rv1211 exhibited an elution property typical of a natively unfolded protein. Subsequent circular dichroism experiments with temperature elevation and trifluoroethanol treatment showed that Rv1211 has unfolded structure. Additional NMR experiment confirmed the unfolded state of the protein and further showed that it does not bind to Ca2+. Still, Rv1211 did bind to trifluoperazine, as evidenced by the two-dimensional NMR spectra of 15N-labeled Rv1211. However, there were no peak shifts upon binding, showing that Rv1211 retained its unfolded state even after the trifluoperazine binding. The residues involved in the binding were clustered in the C-terminal region, as identified by the sequence assignment. Isothermal titration calorimetry showed that the Kd of trifluoperazine-Rv1211 binding is 41 μM and that the stoichiometry is 1 : 2 (Rv1211: trifluoperazine). Our results argue against the suggestion of Rv1211 as a Ca2+-binding calmodulin-like protein, and show that Rv1211 is a natively unfolded protein that binds to trifluoperazine. In addition, our results suggest the evidence of the "Fuzziness" in the Rv1211-trifluoperazine interaction that differs from the conventional binding-induced folding of natively unfolded proteins.
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Affiliation(s)
- Munki Choo
- Natural Product Research Institute, College of Pharmacy, Seoul National University, Gwanak-Ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea
| | - Sehyun Oh
- Natural Product Research Institute, College of Pharmacy, Seoul National University, Gwanak-Ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea
| | - Sihyang Jo
- Natural Product Research Institute, College of Pharmacy, Seoul National University, Gwanak-Ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea
| | - Xing Jin
- Natural Product Research Institute, College of Pharmacy, Seoul National University, Gwanak-Ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea
| | - Yonghyun Song
- Department of Biochemistry, Inha University Hospital, College of Medicine, Inha University, Incheon, 22212, Republic of Korea
| | - He Wen
- Department of Biochemistry and Molecular Biology, School of Medicine, Shenzhen University, Shenzhen, 518060, China
| | - Sunghyouk Park
- Natural Product Research Institute, College of Pharmacy, Seoul National University, Gwanak-Ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea.
| | - Sunmi Kang
- Natural Product Research Institute, College of Pharmacy, Seoul National University, Gwanak-Ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea.
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2
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Mitra G. Emerging Role of Mass Spectrometry-Based Structural Proteomics in Elucidating Intrinsic Disorder in Proteins. Proteomics 2020; 21:e2000011. [PMID: 32959512 DOI: 10.1002/pmic.202000011] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Revised: 06/30/2020] [Indexed: 12/14/2022]
Abstract
Inherent disorder is an integral part of all proteomes, represented as fully or partially unfolded proteins. The lack of order in intrinsically disordered proteins (IDPs) results in an incredibly flexible, floppy, and heterogeneous ensemble, contrary to the well-structured and unique organization of folded proteins. Despite such unusual demeanor, IDPs are crucial for numerous cellular processes and are increasingly being associated with disease-causing pathologies. These warrant more intensive investigation of this atypical class of protein. Traditional biophysical tools, however, fall short of analyzing IDPs, thus making their structure-function characterization challenging. Mass spectrometry (MS) in recent years has evolved as a valuable tool for elucidating the unusual conformational facets of IDPs. In this review, the features of advanced MS techniques such as Hydrogen-deuterium exchange (HDX)-MS, native MS, limited proteolysis (LiP)-MS, chemical cross-linking (XL)-MS, and Fast photochemical oxidation of proteins (FPOP)-MS are briefly discussed. Recent MS studies on IDPs and the unique advantages/shortfalls associated with the above methods while evaluating structural proteomics of IDPs, are illustrated. Eventually the future scope of the MS methods in further decoding the unexplored landscapes of IDPs is presented.
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Affiliation(s)
- Gopa Mitra
- Clinical Proteomics Unit, Division of Molecular Medicine, St. John's Research Institute, St John's Medical College, St. John's National Academy of Health Sciences, 100 Feet Road, Koramangala, Bangalore, Karnataka, 560034, India
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3
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Jebarupa B, Mathew B, Srinivasu BY, Sasikumaran A, Joseph S, Mandal AK, Thomas T, Mitra G. Understanding molecular features of aggregation-resistant tau conformer using oxidized monomer. Biochim Biophys Acta Gen Subj 2019; 1863:993-1005. [DOI: 10.1016/j.bbagen.2019.03.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 02/12/2019] [Accepted: 03/06/2019] [Indexed: 10/27/2022]
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4
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Johnson OT, Kaur T, Garner AL. A Conditionally Fluorescent Peptide Reporter of Secondary Structure Modulation. Chembiochem 2019; 20:40-45. [PMID: 30137694 PMCID: PMC6482830 DOI: 10.1002/cbic.201800377] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Indexed: 12/12/2022]
Abstract
Proteins containing intrinsic disorder often form secondary structure upon interaction with a binding partner. Modulating such structures presents an approach for manipulating the resultant functional outcomes. Translational repressor protein 4E-BP1 is an example of an intrinsically disordered protein that forms an α-helix upon binding to its protein ligand, eIF4E. Current biophysical methods for analyzing binding-induced structural changes are low-throughput, require large amounts of sample, or are extremely sensitive to signal interference by the ligand itself. Herein, we describe the discovery and development of a conditionally fluorescent 4E-BP1 peptide that reports structural changes of its helix in high-throughput format. This reporter peptide is based on conditional quenching of fluorescein by thioamides. In this case, fluorescence signal increases as the peptide becomes more ordered. Conversely, destabilization of the α-helix results in decreased fluorescence signal. The low concentration and low volume of peptide required make this approach amenable for high-throughput screening to discover ligands that alter peptide secondary structure.
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Affiliation(s)
- Oleta T. Johnson
- Program in Chemical Biology, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109 (USA),
| | - Tanpreet Kaur
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, 1600 Huron Parkway, NCRC B520, Ann Arbor, MI 48109 (USA)
| | - Amanda L. Garner
- Program in Chemical Biology, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109 (USA),
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, 1600 Huron Parkway, NCRC B520, Ann Arbor, MI 48109 (USA)
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5
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Jebarupa B, Muralidharan M, Srinivasu BY, Mandal AK, Mitra G. Effect of altered solution conditions on tau conformational dynamics: Plausible implication on order propensity and aggregation. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1866:668-679. [DOI: 10.1016/j.bbapap.2018.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 04/03/2018] [Accepted: 04/05/2018] [Indexed: 01/23/2023]
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6
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Anhydrous polymer-based coating with sustainable controlled release functionality for facile, efficacious impregnation, and delivery of antimicrobial peptides. Biotechnol Bioeng 2018; 115:2000-2012. [DOI: 10.1002/bit.26713] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 03/28/2018] [Accepted: 04/09/2018] [Indexed: 12/28/2022]
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7
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Prates ET, Guan X, Li Y, Wang X, Chaffey PK, Skaf MS, Crowley MF, Tan Z, Beckham GT. The impact of O-glycan chemistry on the stability of intrinsically disordered proteins. Chem Sci 2018; 9:3710-3715. [PMID: 29780502 PMCID: PMC5939190 DOI: 10.1039/c7sc05016j] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 03/19/2018] [Indexed: 01/14/2023] Open
Abstract
Protein glycosylation is a diverse post-translational modification that serves myriad biological functions. O-linked glycans in particular vary widely in extent and chemistry in eukaryotes, with secreted proteins from fungi and yeast commonly exhibiting O-mannosylation in intrinsically disordered regions of proteins, likely for proteolysis protection, among other functions. However, it is not well understood why mannose is often the preferred glycan, and more generally, if the neighboring protein sequence and glycan have coevolved to protect against proteolysis in glycosylated intrinsically disordered proteins (IDPs). Here, we synthesized variants of a model IDP, specifically a natively O-mannosylated linker from a fungal enzyme, with α-O-linked mannose, glucose, and galactose moieties, along with a non-glycosylated linker. Upon exposure to thermolysin, O-mannosylation, by far, provides the highest extent of proteolysis protection. To explain this observation, extensive molecular dynamics simulations were conducted, revealing that the axial configuration of the C2-hydroxyl group (2-OH) of α-mannose adjacent to the glycan-peptide bond strongly influences the conformational features of the linker. Specifically, α-mannose restricts the torsions of the IDP main chain more than other glycans whose equatorial 2-OH groups exhibit interactions that favor perpendicular glycan-protein backbone orientation. We suggest that IDP stiffening due to O-mannosylation impairs protease action, with contributions from protein-glycan interactions, protein flexibility, and protein stability. Our results further imply that resistance to proteolysis is an important driving force for evolutionary selection of α-mannose in eukaryotic IDPs, and more broadly, that glycan motifs for proteolysis protection likely coevolve with the protein sequence to which they attach.
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Affiliation(s)
- Erica T Prates
- National Bioenergy Center , National Renewable Energy Laboratory , Golden , CO 80403 , USA .
- Institute of Chemistry , Center for Computational Engineering and Sciences , University of Campinas , 13084-862 , SP , Brazil
| | - Xiaoyang Guan
- Department of Chemistry and Biochemistry and BioFrontiers Institute , University of Colorado , Boulder , CO 80303 , USA .
| | - Yaohao Li
- Department of Chemistry and Biochemistry and BioFrontiers Institute , University of Colorado , Boulder , CO 80303 , USA .
| | - Xinfeng Wang
- Department of Chemistry and Biochemistry and BioFrontiers Institute , University of Colorado , Boulder , CO 80303 , USA .
| | - Patrick K Chaffey
- Department of Chemistry and Biochemistry and BioFrontiers Institute , University of Colorado , Boulder , CO 80303 , USA .
| | - Munir S Skaf
- Institute of Chemistry , Center for Computational Engineering and Sciences , University of Campinas , 13084-862 , SP , Brazil
| | - Michael F Crowley
- Biosciences Center , National Renewable Energy Laboratory , Golden , CO 80403 , USA .
| | - Zhongping Tan
- Department of Chemistry and Biochemistry and BioFrontiers Institute , University of Colorado , Boulder , CO 80303 , USA .
| | - Gregg T Beckham
- National Bioenergy Center , National Renewable Energy Laboratory , Golden , CO 80403 , USA .
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DeForte S, Uversky VN. Quarterly intrinsic disorder digest (April-May-June, 2014). INTRINSICALLY DISORDERED PROTEINS 2017; 5:e1287505. [PMID: 28321370 DOI: 10.1080/21690707.2017.1287505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This is the 6th issue of the Digested Disorder series that continues to use only 2 criteria for inclusion of a paper to this digest: The publication date (a paper should be published within the covered time frame) and the topic (a paper should be dedicated to any aspect of protein intrinsic disorder). The current digest issue covers papers published during the second quarter of 2014; i.e., during the period of April, May, and June of 2014. Similar to previous issues, the papers are grouped hierarchically by topics they cover, and for each of the included papers a short description is given on its major findings.
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Affiliation(s)
- Shelly DeForte
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA; Département De Biochimie and Centre Robert-Cedergren, Bio-Informatique et Génomique, Université de Montréal, Succursale Centre-Ville, Montreal, Quebec, Canada
| | - Vladimir N Uversky
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA; USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, USA; Laboratory of New Methods in Biology, Institute of Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow Region, Russia; Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
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Structural coalescence underlies the aggregation propensity of a β-barrel protein motif. PLoS One 2017; 12:e0170607. [PMID: 28187186 PMCID: PMC5302452 DOI: 10.1371/journal.pone.0170607] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 01/07/2017] [Indexed: 02/07/2023] Open
Abstract
A clear understanding of the structural foundations underlying protein aggregation is an elusive goal of central biomedical importance. A step toward this aim is exemplified by the β-barrel motif represented by the intestinal fatty acid binding protein (IFABP) and two abridged all-β sheet forms (Δ98Δ and Δ78Δ). At odds with the established notion that a perturbation of the native fold should necessarily favor a buildup of intermediate forms with an enhanced tendency to aggregate, the intrinsic stability (ΔG°H2O) of these proteins does not bear a straightforward correlation with their trifluoroethanol (TFE)-induced aggregation propensity. In view of this fact, we found it more insightful to delve into the connection between structure and stability under sub-aggregating conditions (10% TFE). In the absence of the co-solvent, the abridged variants display a common native-like region decorated with a disordered C-terminal stretch. Upon TFE addition, an increase in secondary structure content is observed, assimilating them to the parent protein. In this sense, TFE perturbs a common native like region while exerting a global compaction effect. Importantly, in all cases, fatty acid binding function is preserved. Interestingly, energetic as well as structural diversity in aqueous solution evolves into a common conformational ensemble more akin in stability. These facts reconcile apparent paradoxical findings related to stability and rates of aggregation. This scenario likely mimics the accrual of aggregation-prone species in the population, an early critical event for the development of fibrillation.
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10
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Bioanalytical approaches to assess the proteolytic stability of therapeutic fusion proteins. Bioanalysis 2015; 7:3035-51. [DOI: 10.4155/bio.15.217] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Therapeutic fusion proteins (TFPs) are designed to improve the therapeutic profile of an endogenous protein or protein fragment with a limited dose frequency providing the desired pharmacological activity in vivo. Fusion of a therapeutic protein to a half-life extension or targeting domain can improve the disposition of the molecule or introduce a novel mechanism of action. Prolonged exposure and altered biodistribution of an endogenous protein through fusion technology increases the potential for local protein unfolding during circulation increasing the chance for partial proteolysis of the therapeutic domain. Characterizing the proteolytic liabilities of a TFP can guide engineering efforts to inhibit or hinder partial proteolysis. This review focuses on considerations and techniques for evaluating the stability of a TFP both in vivo and in vitro.
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Dong J, Bruening ML. Functionalizing Microporous Membranes for Protein Purification and Protein Digestion. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2015; 8:81-100. [PMID: 26001953 DOI: 10.1146/annurev-anchem-071114-040255] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This review examines advances in the functionalization of microporous membranes for protein purification and the development of protease-containing membranes for controlled protein digestion prior to mass spectrometry analysis. Recent studies confirm that membranes are superior to bead-based columns for rapid protein capture, presumably because convective mass transport in membrane pores rapidly brings proteins to binding sites. Modification of porous membranes with functional polymeric films or TiO₂ nanoparticles yields materials that selectively capture species ranging from phosphopeptides to His-tagged proteins, and protein-binding capacities often exceed those of commercial beads. Thin membranes also provide a convenient framework for creating enzyme-containing reactors that afford control over residence times. With millisecond residence times, reactors with immobilized proteases limit protein digestion to increase sequence coverage in mass spectrometry analysis and facilitate elucidation of protein structures. This review emphasizes the advantages of membrane-based techniques and concludes with some challenges for their practical application.
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Affiliation(s)
- Jinlan Dong
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824;
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12
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Hackl EV. Effect of Temperature on the Conformation of Natively Unfolded Protein 4E-BP1 in Aqueous and Mixed Solutions Containing Trifluoroethanol and Hexafluoroisopropanol. Protein J 2014; 34:18-28. [DOI: 10.1007/s10930-014-9595-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Rivera-Najera LY, Saab-Rincón G, Battaglia M, Amero C, Pulido NO, García-Hernández E, Solórzano RM, Reyes JL, Covarrubias AA. A group 6 late embryogenesis abundant protein from common bean is a disordered protein with extended helical structure and oligomer-forming properties. J Biol Chem 2014; 289:31995-32009. [PMID: 25271167 DOI: 10.1074/jbc.m114.583369] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Late embryogenesis-abundant proteins accumulate to high levels in dry seeds. Some of them also accumulate in response to water deficit in vegetative tissues, which leads to a remarkable association between their presence and low water availability conditions. A major sub-group of these proteins, also known as typical LEA proteins, shows high hydrophilicity and a high percentage of glycine and other small amino acid residues, distinctive physicochemical properties that predict a high content of structural disorder. Although all typical LEA proteins share these characteristics, seven groups can be distinguished by sequence similarity, indicating structural and functional diversity among them. Some of these groups have been extensively studied; however, others require a more detailed analysis to advance in their functional understanding. In this work, we report the structural characterization of a group 6 LEA protein from a common bean (Phaseolus vulgaris L.) (PvLEA6) by circular dichroism and nuclear magnetic resonance showing that it is a disordered protein in aqueous solution. Using the same techniques, we show that despite its unstructured nature, the addition of trifluoroethanol exhibited an intrinsic potential in this protein to gain helicity. This property was also promoted by high osmotic potentials or molecular crowding. Furthermore, we demonstrate that PvLEA6 protein is able to form soluble homo-oligomeric complexes that also show high levels of structural disorder. The association between PvLEA6 monomers to form dimers was shown to occur in plant cells by bimolecular fluorescence complementation, pointing to the in vivo functional relevance of this association.
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Affiliation(s)
- Lucero Y Rivera-Najera
- Departamentos de Biología Molecular de Plantas and Universidad Nacional Autónoma de México, Apdo. Postal 510-3, 62250 Cuernavaca, Mor
| | - Gloria Saab-Rincón
- Departamentos de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, 62250 Cuernavaca, Mor
| | - Marina Battaglia
- Departamentos de Biología Molecular de Plantas and Universidad Nacional Autónoma de México, Apdo. Postal 510-3, 62250 Cuernavaca, Mor
| | - Carlos Amero
- Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Av. Universidad No. 1001, Col Chamilpa, 62209 Cuernavaca, Morelos, and
| | - Nancy O Pulido
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México 04510, D. F. México
| | - Enrique García-Hernández
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México 04510, D. F. México
| | - Rosa M Solórzano
- Departamentos de Biología Molecular de Plantas and Universidad Nacional Autónoma de México, Apdo. Postal 510-3, 62250 Cuernavaca, Mor
| | - José L Reyes
- Departamentos de Biología Molecular de Plantas and Universidad Nacional Autónoma de México, Apdo. Postal 510-3, 62250 Cuernavaca, Mor
| | - Alejandra A Covarrubias
- Departamentos de Biología Molecular de Plantas and Universidad Nacional Autónoma de México, Apdo. Postal 510-3, 62250 Cuernavaca, Mor..
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Specificity of O-glycosylation in enhancing the stability and cellulose binding affinity of Family 1 carbohydrate-binding modules. Proc Natl Acad Sci U S A 2014; 111:7612-7. [PMID: 24821760 DOI: 10.1073/pnas.1402518111] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The majority of biological turnover of lignocellulosic biomass in nature is conducted by fungi, which commonly use Family 1 carbohydrate-binding modules (CBMs) for targeting enzymes to cellulose. Family 1 CBMs are glycosylated, but the effects of glycosylation on CBM function remain unknown. Here, the effects of O-mannosylation are examined on the Family 1 CBM from the Trichoderma reesei Family 7 cellobiohydrolase at three glycosylation sites. To enable this work, a procedure to synthesize glycosylated Family 1 CBMs was developed. Subsequently, a library of 20 CBMs was synthesized with mono-, di-, or trisaccharides at each site for comparison of binding affinity, proteolytic stability, and thermostability. The results show that, although CBM mannosylation does not induce major conformational changes, it can increase the thermolysin cleavage resistance up to 50-fold depending on the number of mannose units on the CBM and the attachment site. O-Mannosylation also increases the thermostability of CBM glycoforms up to 16 °C, and a mannose disaccharide at Ser3 seems to have the largest themostabilizing effect. Interestingly, the glycoforms with small glycans at each site displayed higher binding affinities for crystalline cellulose, and the glycoform with a single mannose at each of three positions conferred the highest affinity enhancement of 7.4-fold. Overall, by combining chemical glycoprotein synthesis and functional studies, we show that specific glycosylation events confer multiple beneficial properties on Family 1 CBMs.
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