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Shoemaker KR, Kim PS, Brems DN, Marqusee S, York EJ, Chaiken IM, Stewart JM, Baldwin RL. Nature of the charged-group effect on the stability of the C-peptide helix. Proc Natl Acad Sci U S A 1985; 82:2349-53. [PMID: 3857585 PMCID: PMC397555 DOI: 10.1073/pnas.82.8.2349] [Citation(s) in RCA: 227] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The residues responsible for the pH-dependent stability of the helix formed by the isolated C-peptide (residues 1-13 of ribonuclease A) have been identified by chemical synthesis of analogues and measurement of their helix-forming properties. Each of the residues ionizing between pH 2 and pH 8 has been replaced separately by an uncharged residue. Protonation of Glu-2- is responsible for the sharp decrease in helix stability between pH 5 and pH 2, and deprotonation of His-12+ causes a similar decrease between pH 5 and pH 8. Glu-9- is not needed for helix stability. The results cannot be explained by the Zimm-Bragg model and host-guest data for alpha-helix formation, which predict that the stability of the C-peptide helix should increase when Glu-2- is protonated or when His-12+ is deprotonated. Moreover, histidine+ is a strong helix-breaker in host-guest studies. In proteins, acidic and basic residues tend to occur at opposite ends of alpha-helices: acidic residues occur preferentially near the NH2-terminal end and basic residues near the COOH-terminal end. A possible explanation, based on a helix dipole model, has been given [Blagdon, D. E. & Goodman, M. (1975) Biopolymers 14, 241-245]. Our results are consistent with the helix dipole model and they support the suggestion that the distribution of charged residues in protein helices reflects the helix-stabilizing propensity of those residues. Because Glu-9 is not needed for helix stability, a possible Glu-9-...His-12+ salt bridge does not contribute significantly to helix stability. The role of a possible Glu-2-...Arg-10+ salt bridge has not yet been evaluated. A charged-group effect on alpha-helix stability in water has also been observed in a different peptide system [Ihara, S., Ooi, T. & Takahashi, S. (1982) Biopolymers 21, 131-145]: block copolymers containing (Ala)20 and (Glu)20 show partial helix formation at low temperatures, pH 7.5, where the glutamic acid residues are ionized. (Glu)20(Ala)20Phe forms a helix that is markedly more stable than (Ala)20(Glu)20Phe. The results are consistent with a helix dipole model.
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Thirumangalathu R, Krishnan S, Ricci MS, Brems DN, Randolph TW, Carpenter JF. Silicone oil- and agitation-induced aggregation of a monoclonal antibody in aqueous solution. J Pharm Sci 2009; 98:3167-81. [PMID: 19360857 PMCID: PMC2751612 DOI: 10.1002/jps.21719] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Silicone oil, which is used as a lubricant or coating in devices such as syringes, needles and pharmaceutical containers, has been implicated in aggregation and particulation of proteins and antibodies. Aggregation of therapeutic protein products induced by silicone oil can pose a challenge to their development and commercialization. To systematically characterize the role of silicone oil on protein aggregation, the effects of agitation, temperature, pH, and ionic strength on silicone oil-induced loss of monomeric anti-streptavidin IgG 1 antibody were examined. Additionally, the influences of excipients polysorbate 20 and sucrose on protein aggregation were investigated. In the absence of agitation, protein absorbed to silicone oil with approximately monolayer coverage, however silicone oil did not stimulate aggregation during isothermal incubation unless samples were also agitated. A synergistic stimulation of aggregation by a combination of agitation and silicone oil was observed. Solution conditions which reduced colloidal stability of the antibody, as assessed by determination of osmotic second virial coefficients, accelerated aggregation during agitation with silicone oil. Polysorbate 20 completely inhibited silicone oil-induced monomer loss during agitation. A formulation strategy involving optimization of colloidal stability of the antibody as well as incorporation of surfactants such as polysorbate 20 is proposed to reduce silicone oil-induced aggregation of therapeutic protein products.
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Research Support, N.I.H., Extramural |
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208 |
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Liu D, Ren D, Huang H, Dankberg J, Rosenfeld R, Cocco MJ, Li L, Brems DN, Remmele RL. Structure and Stability Changes of Human IgG1 Fc as a Consequence of Methionine Oxidation. Biochemistry 2008; 47:5088-100. [DOI: 10.1021/bi702238b] [Citation(s) in RCA: 195] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17 |
195 |
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Kinstler OB, Brems DN, Lauren SL, Paige AG, Hamburger JB, Treuheit MJ. Characterization and stability of N-terminally PEGylated rhG-CSF. Pharm Res 1996; 13:996-1002. [PMID: 8842035 DOI: 10.1023/a:1016042220817] [Citation(s) in RCA: 171] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
PURPOSE The liquid stability of rhG-CSF was investigated after polyethylene glycol (PEG) with an average molecular weight of 6000 daltons was covalently attached to the N-terminal methionine residue. METHODS The conjugation methods chosen for modifying the N-terminal residue were alkylation and acylation. The N-terminally PEGylated rhG-CSF conjugates were purified by cation exchange chromatography. The physical characterization methods of SDS-PAGE, endoproteinase peptide mapping, circular dichroism and in-vivo bioassay were used to test for differences between the PEG-rhG-CSF molecules. RESULTS Physical characterization indicated no apparent differences in the rhG-CSF molecules that were conjugated with either method. Stability, in liquid at elevated temperatures, of these conjugated molecules indicated that the primary pathway of degradation was aggregation. Conjugation through alkylation offered the distinct advantage of decreasing, by approximately 5 times, the amount of aggregation present as compared to acylation. CONCLUSIONS We suggest, that the increased stability observed for the molecules utilizing the alkylation conjugation method may be due to the preservation of charge on the alpha amino group of rhG-CSF.
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Comparative Study |
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Ren D, Pipes GD, Liu D, Shih LY, Nichols AC, Treuheit MJ, Brems DN, Bondarenko PV. An improved trypsin digestion method minimizes digestion-induced modifications on proteins. Anal Biochem 2009; 392:12-21. [DOI: 10.1016/j.ab.2009.05.018] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Revised: 05/11/2009] [Accepted: 05/12/2009] [Indexed: 11/25/2022]
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148 |
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Brems DN, Alter LA, Beckage MJ, Chance RE, DiMarchi RD, Green LK, Long HB, Pekar AH, Shields JE, Frank BH. Altering the association properties of insulin by amino acid replacement. PROTEIN ENGINEERING 1992; 5:527-33. [PMID: 1438163 DOI: 10.1093/protein/5.6.527] [Citation(s) in RCA: 147] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The importance of ProB28 and LysB29 on the self-association of insulin was established by systematically truncating the C terminus of the B chain. The relationship between structure and association was further explored by making numerous amino acid replacements at B28 and B29. Association was studied by circular dichroism, size-exclusion chromatography and ultracentrifugation. Our results show that the location of a prolyl residue at B28 is critical for high-affinity self-association. Removal of ProB28 in a series of C-terminal truncated insulins, or amino acid replacement of ProB28, greatly reduced association. The largest disruption to association was achieved by replacing LysB29 with Pro and varying the amino acid at B28. Several of the analogs were predominantly monomers in solutions up to 3 mg/ml. These amino acid substitutions decreased association by primarily disrupting the formation of dimers. Such amino acid substitutions also substantially reduced the Zn-induced insulin hexamer formation. The formation of monomeric insulins through amino acid replacements was accompanied by conformational changes that may be the cause for decreased association. It is demonstrated that self-association of insulin can be drastically altered by substitution of one or two key amino acids.
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Abstract
PURPOSE To determine the effect of protein concentration on aggregation induced through quiescent shelf-life incubation or shipping-related agitation. METHODS All aggregation was measured by size-exclusion high-performance liquid chromatography. Aggregation was induced by time-dependent incubation under stationary conditions or by agitation caused by shaking, vortexing, or vibration using simulated shipping conditions. RESULTS Protein aggregation is commonly a second- or higher-order process that is expected to increase with higher protein concentration. As expected, for three proteins (PEG-GCSF, PEG-MGDF, and OPG-Fc) that were examined, the aggregation increased with higher protein concentration if incubated in a quiescent shelf-life setting. However, aggregation decreased with higher protein concentration if induced by an air/water interface as a result of agitation. This unexpected result may be explained by the rate-limiting effect on aggregation of the air/water interface and the critical nature of the air/ water interface to protein ratio that is greatest with decreased protein concentration. The non-ionic detergent polysorbate 20 enhanced the aggregation observed in the quiescently incubated sample but abrogated the aggregation induced by the air/water interface. CONCLUSIONS The effect of protein concentration was opposite for aggregation that resulted from quiescent shelf-life treatment compared to induction by agitation. For motionless shelf-life incubation, increased concentration of protein resulted in more aggregation. However, exposure to agitation resulted in more aggregation with decreased protein concentration. These results highlight an unexpected complexity of protein aggregation reactions.
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Saluja A, Fesinmeyer RM, Hogan S, Brems DN, Gokarn YR. Diffusion and sedimentation interaction parameters for measuring the second virial coefficient and their utility as predictors of protein aggregation. Biophys J 2011; 99:2657-65. [PMID: 20959107 DOI: 10.1016/j.bpj.2010.08.020] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 08/05/2010] [Accepted: 08/10/2010] [Indexed: 12/28/2022] Open
Abstract
The concentration-dependence of the diffusion and sedimentation coefficients (k(D) and k(s), respectively) of a protein can be used to determine the second virial coefficient (B₂), a parameter valuable in predicting protein-protein interactions. Accurate measurement of B₂ under physiologically and pharmaceutically relevant conditions, however, requires independent measurement of k(D) and k(s) via orthogonal techniques. We demonstrate this by utilizing sedimentation velocity (SV) and dynamic light scattering (DLS) to analyze solutions of hen-egg white lysozyme (HEWL) and a monoclonal antibody (mAb1) in different salt solutions. The accuracy of the SV-DLS method was established by comparing measured and literature B₂ values for HEWL. In contrast to the assumptions necessary for determining k(D) and k(s) via SV alone, k(D) and ks were of comparable magnitudes, and solution conditions were noted for both HEWL and mAb1 under which 1), k(D) and k(s) assumed opposite signs; and 2), k(D) ≥k(s). Further, we demonstrate the utility of k(D) and k(s) as qualitative predictors of protein aggregation through agitation and accelerated stability studies. Aggregation of mAb1 correlated well with B₂, k(D), and k(s), thus establishing the potential for k(D) to serve as a high-throughput predictor of protein aggregation.
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Journal Article |
14 |
121 |
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Gokarn YR, Fesinmeyer RM, Saluja A, Razinkov V, Chase SF, Laue TM, Brems DN. Effective charge measurements reveal selective and preferential accumulation of anions, but not cations, at the protein surface in dilute salt solutions. Protein Sci 2011; 20:580-7. [PMID: 21432935 DOI: 10.1002/pro.591] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Specific-ion effects are ubiquitous in nature; however, their underlying mechanisms remain elusive. Although Hofmeister-ion effects on proteins are observed at higher (>0.3 M) salt concentrations, in dilute (<0.1 M) salt solutions nonspecific electrostatic screening is considered to be dominant. Here, using effective charge (Q*) measurements of hen-egg white lysozyme (HEWL) as a direct and differential measure of ion-association, we experimentally show that anions selectively and preferentially accumulate at the protein surface even at low (<100 mM) salt concentrations. At a given ion normality (50 mN), the HEWL Q* was dependent on anion, but not cation (Li(+), Na(+), K(+), Rb(+), Cs(+), GdnH(+), and Ca(2+)), identity. The Q* decreased in the order F(-) > Cl(-) > Br(-) > NO(3)(-) ∼ I(-) > SCN(-) > ClO(4)(-) ≫ SO(4)(2-), demonstrating progressively greater binding of the monovalent anions to HEWL and also show that the SO(4)(2-) anion, despite being strongly hydrated, interacts directly with the HEWL surface. Under our experimental conditions, we observe a remarkable asymmetry between anions and cations in their interactions with the HEWL surface.
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Journal Article |
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Rajan RS, Li T, Aras M, Sloey C, Sutherland W, Arai H, Briddell R, Kinstler O, Lueras AMK, Zhang Y, Yeghnazar H, Treuheit M, Brems DN. Modulation of protein aggregation by polyethylene glycol conjugation: GCSF as a case study. Protein Sci 2006; 15:1063-75. [PMID: 16597829 PMCID: PMC2242524 DOI: 10.1110/ps.052004006] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 02/03/2006] [Accepted: 02/09/2006] [Indexed: 10/24/2022]
Abstract
Polyethylene glycol (PEG) conjugation to proteins has emerged as an important technology to produce drug molecules with sustained duration in the body. However, the implications of PEG conjugation to protein aggregation have not been well understood. In this study, conducted under physiological pH and temperature, N-terminal attachment of a 20 kDa PEG moiety to GCSF had the ability to (1) prevent protein precipitation by rendering the aggregates soluble, and (2) slow the rate of aggregation relative to GCSF. Our data suggest that PEG-GCSF solubility was mediated by favorable solvation of water molecules around the PEG group. PEG-GCSF appeared to aggregate on the same pathway as that of GCSF, as evidenced by (a) almost identical secondary structural transitions accompanying aggregation, (b) almost identical covalent character in the aggregates, and (c) the ability of PEG-GCSF to rescue GCSF precipitation. To understand the role of PEG length, the aggregation properties of free GCSF were compared to 5kPEG-GCSF and 20kPEG-GCSF. It was observed that even 5kPEG-GCSF avoided precipitation by forming soluble aggregates, and the stability toward aggregation was vastly improved compared to GCSF, but only marginally less stable than the 20kPEG-GCSF. Biological activity measurements demonstrated that both 5kPEG-GCSF and 20kPEG-GCSF retained greater activity after incubation at physiological conditions than free GCSF, consistent with the stability measurements. The data is most compatible with a model where PEG conjugation preserves the mechanism underlying protein aggregation in GCSF, steric hindrance by PEG influences aggregation rate, while aqueous solubility is mediated by polar PEG groups on the aggregate surface.
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Evaluation Study |
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Rehder DS, Chelius D, McAuley A, Dillon TM, Xiao G, Crouse-Zeineddini J, Vardanyan L, Perico N, Mukku V, Brems DN, Matsumura M, Bondarenko PV. Isomerization of a single aspartyl residue of anti-epidermal growth factor receptor immunoglobulin gamma2 antibody highlights the role avidity plays in antibody activity. Biochemistry 2008; 47:2518-30. [PMID: 18232715 DOI: 10.1021/bi7018223] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new isoform of the light chain of a fully human monoclonal immunoglobulin gamma2 (IgG2) antibody panitumumab against human epidermal growth factor receptor (EGFR) was generated by in vitro aging. The isoform was attributed to the isomerization of aspartate 92 located between phenylalanine 91 and histidine 93 residues in the antigen-binding region. The isomerization rate increased with increased temperature and decreased pH. A size-exclusion chromatography binding assay was used to show that one antibody molecule was able to bind two soluble extracellular EGFR molecules in solution, and isomerization of one or both Asp-92 residues deactivated one or both antigen-binding regions, respectively. In addition, isomerization of Asp-92 showed a decrease in in vitro potency as measured by a cell proliferation assay with a 32D cell line that expressed the full-length human EGFR. The data indicate that antibodies containing either one or two isomerized residues were not effective in inhibiting EGFR-mediated cell proliferation, and that two unmodified antigen binding regions were needed to achieve full efficacy. For comparison, the potency of an intact IgG1 antibody cetuximab against the same receptor was correlated with the bioactivity of its individual antigen-binding fragments. The intact IgG1 antibody with two antigen-binding fragments was also much more active in suppressing cell proliferation than the individual fragments, similar to the IgG2 results. These results indicated that avidity played a key role in the inhibition of cell proliferation by these antibodies against the human EGFR, suggesting that their mechanisms of action are similar.
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Journal Article |
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Raso SW, Abel J, Barnes JM, Maloney KM, Pipes G, Treuheit MJ, King J, Brems DN. Aggregation of granulocyte-colony stimulating factor in vitro involves a conformationally altered monomeric state. Protein Sci 2005; 14:2246-57. [PMID: 16131655 PMCID: PMC2253479 DOI: 10.1110/ps.051489405] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Revised: 03/31/2005] [Accepted: 06/17/2005] [Indexed: 10/25/2022]
Abstract
Aggregation of partially folded intermediates populated during protein folding processes has been described for many proteins. Likewise, partially unfolded chains, generated by perturbation of numerous proteins by heat or chemical denaturants, have also been shown to aggregate readily. However, the process of protein aggregation from native-state conditions is less well understood. Granulocyte-colony stimulating factor (G-CSF), a member of the four-helix bundle class of cytokines, is a therapeutically relevant protein involved in stimulating the growth and maturation of phagocytotic white blood cells. Under native-like conditions (37 degrees C [pH 7.0]), G-CSF shows a significant propensity to aggregate. Our data suggest that under these conditions, native G-CSF exists in equilibrium with an altered conformation, which is highly aggregation prone. This species is enriched in 1-2 M GdmCl, as determined by tryptophan fluorescence and increased aggregation kinetics. In particular, specific changes in Trp58 fluorescence report a local rearrangement in the large loop region between helices A and B. However, circular dichroism, reactivity toward cyanylation, and ANS binding demonstrate that this conformational change is subtle, having no substantial disruption of secondary and tertiary structure, reactivity of the free sulfhydryl at Cys17 or exposure of buried hydrophobic regions. There is no indication that this altered conformation is important to biological activity, making it an attractive target for rational protein stabilization.
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Research Support, N.I.H., Extramural |
20 |
83 |
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McAuley A, Jacob J, Kolvenbach CG, Westland K, Lee HJ, Brych SR, Rehder D, Kleemann GR, Brems DN, Matsumura M. Contributions of a disulfide bond to the structure, stability, and dimerization of human IgG1 antibody CH3 domain. Protein Sci 2008; 17:95-106. [PMID: 18156469 DOI: 10.1110/ps.073134408] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Recombinant human monoclonal antibodies have become important protein-based therapeutics for the treatment of various diseases. The antibody structure is complex, consisting of beta-sheet rich domains stabilized by multiple disulfide bridges. The dimerization of the C(H)3 domain in the constant region of the heavy chain plays a pivotal role in the assembly of an antibody. This domain contains a single buried, highly conserved disulfide bond. This disulfide bond was not required for dimerization, since a recombinant human C(H)3 domain, even in the reduced state, existed as a dimer. Spectroscopic analyses showed that the secondary and tertiary structures of reduced and oxidized C(H)3 dimer were similar, but differences were observed. The reduced C(H)3 dimer was less stable than the oxidized form to denaturation by guanidinium chloride (GdmCl), pH, or heat. Equilibrium sedimentation revealed that the reduced dimer dissociated at lower GdmCl concentration than the oxidized form. This implies that the disulfide bond shifts the monomer-dimer equilibrium. Interestingly, the dimer-monomer dissociation transition occurred at lower GdmCl concentration than the unfolding transition. Thus, disulfide bond formation in the human C(H)3 domain is important for stability and dimerization. Here we show the importance of the role played by the disulfide bond and how it affects the stability and monomer-dimer equilibrium of the human C(H)3 domain. Hence, these results may have implications for the stability of the intact antibody.
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Journal Article |
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81 |
14
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23 |
74 |
15
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Havel HA, Kauffman EW, Plaisted SM, Brems DN. Reversible self-association of bovine growth hormone during equilibrium unfolding. Biochemistry 1986; 25:6533-8. [PMID: 3790540 DOI: 10.1021/bi00369a029] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Previous investigations have shown that bovine growth hormone (bGH, somatotropin) unfolds through a reversible multistate process with at least one stable equilibrium intermediate. In extending our knowledge of the folding process for bGH, we demonstrate that a self-associated form of partially denatured bGH is formed during equilibrium unfolding experiments. The self-associated species has been identified by hydrodynamic measurements (size exclusion high-performance liquid chromatography and static and dynamic light scattering) and by measurements of the bGH concentration dependence of aromatic amino acid spectral properties (fluorescence, second-derivative absorption, and circular dichroism). The apparent maximum concentration for self-association occurs when bGH is partially denatured, i.e., at 3.7 M guanidine hydrochloride or 8.5 M urea, and its formation is reversible. Some of the properties of the self-associated species include quenched tryptophan fluorescence, increased tryptophan circular dichroism intensity at 300 nm, polar tryptophan environment, and a weight-average radius of about 5 nm. The self-association of bGH is mediated by specific intermolecular interactions with little increase in molecular size occurring above the saturation level of 4 mg/mL bGH. These phenomena have important implications for the design and interpretation of folding experiments in vitro and may have physiological consequences.
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69 |
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He F, Becker GW, Litowski JR, Narhi LO, Brems DN, Razinkov VI. High-throughput dynamic light scattering method for measuring viscosity of concentrated protein solutions. Anal Biochem 2010; 399:141-3. [DOI: 10.1016/j.ab.2009.12.003] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 12/01/2009] [Accepted: 12/02/2009] [Indexed: 10/20/2022]
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68 |
17
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Kosky AA, Razzaq UO, Treuheit MJ, Brems DN. The effects of alpha-helix on the stability of Asn residues: deamidation rates in peptides of varying helicity. Protein Sci 1999; 8:2519-23. [PMID: 10595558 PMCID: PMC2144212 DOI: 10.1110/ps.8.11.2519] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Asn deamidation was monitored in Ala-based octadecapeptides of varying alpha-helicity. Gly was substituted for Ala residues at positions 6 and 16 to create a peptide with less helicity. Ala --> Gly substitutions were made at three or more residues from the Asn to negate known primary sequence effects on deamidation rates. The extent of helicity and rate of Asn deamidation for alkaline aqueous solutions of each peptide was measured as a function of temperature by circular dichroism and reversed-phase high-performance liquid chromatography, respectively. The rate of deamidation in the peptides was inversely proportional to the extent of alpha-helicity. The results support the conclusion that Asn deamidation only occurs in the nonhelical population of conformers.
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research-article |
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68 |
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Bakaysa DL, Radziuk J, Havel HA, Brader ML, Li S, Dodd SW, Beals JM, Pekar AH, Brems DN. Physicochemical basis for the rapid time-action of LysB28ProB29-insulin: dissociation of a protein-ligand complex. Protein Sci 1996; 5:2521-31. [PMID: 8976561 PMCID: PMC2143322 DOI: 10.1002/pro.5560051215] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The rate-limiting step for the absorption of insulin solutions after subcutaneous injection is considered to be the dissociation of self-associated hexamers to monomers. To accelerate this absorption process, insulin analogues have been designed that possess full biological activity and yet have greatly diminished tendencies to self-associate. Sedimentation velocity and static light scattering results show that the presence of zinc and phenolic ligands (m-cresol and/or phenol) cause one such insulin analogue, LysB28ProB29-human insulin (LysPro), to associate into a hexameric complex. Most importantly, this ligand-bound hexamer retains its rapid-acting pharmacokinetics and pharmacodynamics. The dissociation of the stabilized hexameric analogue has been studied in vitro using static light scattering as well as in vivo using a female pig pharmacodynamic model. Retention of rapid time-action is hypothesized to be due to altered subunit packing within the hexamer. Evidence for modified monomer-monomer interactions has been observed in the X-ray crystal structure of a zinc LysPro hexamer (Ciszak E et al., 1995, Structure 3:615-622). The solution state behavior of LysPro, reported here, has been interpreted with respect to the crystal structure results. In addition, the phenolic ligand binding differences between LysPro and insulin have been compared using isothermal titrating calorimetry and visible absorption spectroscopy of cobalt-containing hexamers. These studies establish that rapid-acting insulin analogues of this type can be stabilized in solution via the formation of hexamer complexes with altered dissociation properties.
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research-article |
29 |
65 |
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Brems DN, Plaisted SM, Kauffman EW, Havel HA. Characterization of an associated equilibrium folding intermediate of bovine growth hormone. Biochemistry 1986; 25:6539-43. [PMID: 3790541 DOI: 10.1021/bi00369a030] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In the preceding paper [Havel, H. A., Kauffman, E. W., Plaisted, S. M., & Brems, D. N. (1986) Biochemistry (preceding paper in this issue)], an associated intermediate was shown to be highly populated during the equilibrium denaturation of bovine growth hormone. In this paper, we describe its partial characterization and propose a mechanism for association. The associated equilibrium intermediate is populated under conditions that induce partial denaturation and at protein concentrations greater than 0.2 mg/mL. The remaining nativelike helical structure present in the partially denatured species is implicated in the mechanism of association as demonstrated by similar concentration dependencies and thermal stabilities of the helix and the associated equilibrium intermediate. Furthermore, it is suggested that a putative amphiphilic helix from residues 110-127 plays a critical role in the association as demonstrated by a diminution of the associated equilibrium intermediate when mixed with the peptide fragment 96-133. A model is proposed to account for these results in which partial denaturation exposes the segment of the protein corresponding to the hydrophobic face of the putative amphiphilic helix 110-127. This metastable form is the species from which association occurs. Association is stabilized by the hydrophobic interactions resulting from intermolecular packing of the lipophilic faces of the helices. The implications of these results to protein folding studies are described.
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Thirumangalathu R, Krishnan S, Brems DN, Randolph TW, Carpenter JF. Effects of pH, temperature, and sucrose on benzyl alcohol-induced aggregation of recombinant human granulocyte colony stimulating factor. J Pharm Sci 2006; 95:1480-97. [PMID: 16729274 DOI: 10.1002/jps.20619] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Antimicrobial preservatives (e.g., benzyl alcohol), which are required in multidose formulations, can induce protein aggregation. In this study, the mechanism of benzyl alcohol-induced aggregation of recombinant human granulocyte colony-stimulating factor (rhGCSF) was investigated by determining the effects of temperature, pH, and sucrose on this process. rhGCSF was incubated at 25 and 37 degrees C and at pH 7.0 (phosphate-buffered saline, PBS) and pH 3.5 (HCl). Benzyl alcohol (0.9% w/v) accelerated aggregation of rhGCSF at pH 7.0, an effect that was much greater at 37 degrees C than at 25 degrees C and partially counteracted by 1.0 M sucrose. At pH 3.5, benzyl alcohol did not induce aggregation of rhGCSF. Spectroscopic studies showed that 0.9% benzyl alcohol altered the tertiary structure of rhGCSF at both pH, without detectably altering secondary structure. Structural perturbation was greater at 37 degrees C than at 25 degrees C. At both pH 7.0 and 3.5, the hydrogen-deuterium (H-D) exchange rate for rhGCSF was increased by 0.9% benzyl alcohol. Sucrose (1.0 M) partially counteracted the benzyl alcohol-induced perturbation of tertiary structure and the increase in H-D exchange rate. Thus, benzyl alcohol accelerates aggregation of rhGCSF at pH 7.0, because it favors partially unfolded aggregation-prone conformations of the protein. Sucrose partially counteracts benzyl alcohol-induced rhGCSF aggregation by shifting the molecular population away from these species and towards more compact conformations. We postulate that the absence of aggregation at pH 3.5, even with benzyl alcohol-induced structural perturbation, is due to the unfavorable energetics of intermolecular interactions (i.e., colloidal stability) between rhGCSF molecules at this pH.
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Research Support, U.S. Gov't, Non-P.H.S. |
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Brems DN, Plaisted SM, Havel HA, Kauffman EW, Stodola JD, Eaton LC, White RD. Equilibrium denaturation of pituitary- and recombinant-derived bovine growth hormone. Biochemistry 1985; 24:7662-8. [PMID: 4092031 DOI: 10.1021/bi00347a025] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Holladay and co-workers [Holladay, L. A., Hammonds, R. G., & Puett, D. (1974) Biochemistry 13, 1653-1661] reported the presence of an equilibrium intermediate in the guanidine hydrochloride (GdnHCl) induced denaturation of pituitary-derived bovine growth hormone (p-bGH). Since then, numerous reports have appeared demonstrating the inherent heterogeneity in p-bGH. In this report we show that a standard preparation of p-bGH can be separated into two components of almost equal abundance differing in molecular weight by approximately 1000. Each of these two components could give rise to different denaturation transitions which would be interpreted as evidence for equilibrium intermediates. We report here the equilibrium denaturation of bGH produced by Escherichia coli through recombinant DNA technology. The recombinant-derived bGH (r-bGH) is more homogeneous than that derived from pituitary sources and is greater than 95% a single polypeptide entity. Nevertheless, the GdnHCl-induced denaturation profiles of both recombinant bGH and pituitary bGH are very similar. The presence of equilibrium intermediates is verified by the asymmetry of the denaturation transition as measured by size-exclusion high-performance liquid chromatography and by noncoincidence of the denaturation transitions as observed by ultraviolet absorbance, fluorescence intensity, and circular dichroism. These findings conclusively show that the secondary structure of bovine growth hormone is more stable than the tertiary structure and is consistent with a framework model of protein folding.
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Comparative Study |
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Brems DN, Brown PL, Becker GW. Equilibrium denaturation of human growth hormone and its cysteine-modified forms. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39390-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Cheng W, Joshi SB, He F, Brems DN, He B, Kerwin BA, Volkin DB, Middaugh CR. Comparison of High-Throughput Biophysical Methods to Identify Stabilizing Excipients for a Model IgG2 Monoclonal Antibody: Conformational Stability and Kinetic Aggregation Measurements. J Pharm Sci 2012; 101:1701-20. [DOI: 10.1002/jps.23076] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 01/06/2012] [Accepted: 01/18/2012] [Indexed: 12/12/2022]
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Brems DN, Stellwagen E. Manipulation of the observed kinetic phases in the refolding of denatured ferricytochromes c. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32715-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Brems DN, Brown PL, Heckenlaible LA, Frank BH. Equilibrium denaturation of insulin and proinsulin. Biochemistry 1990; 29:9289-93. [PMID: 2271596 DOI: 10.1021/bi00491a026] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The guanidine hydrochloride induced equilibrium denaturation of insulin and proinsulin was studied by using near- and far-ultraviolet (UV) circular dichroism (CD). The denaturation transition of insulin is reversible, cooperative, symmetrical, and the same whether detected by near- or far-UV CD. These results are consistent with a two-state denaturation process without any appreciable equilibrium intermediates. Analysis of the insulin denaturation data yields a Gibbs free energy of unfolding of 4.5 +/- 0.5 kcal/mol. Denaturation of proinsulin detected by near-UV CD appears to be the same as for insulin, but if detected by far-UV CD appears different. The far-UV CD results demonstrate a multiphasic transition with the connecting peptide portion unfolding at lower concentrations of denaturant. Similar studies with the isolated C-peptide show that its conformation and susceptibility to denaturation are independent of the rest of the proinsulin molecule. After the proinsulin denaturation results were adjusted for the connecting peptide contribution, a denaturation transition identical with that of insulin was obtained. These results show that for proinsulin, the connecting peptide segment is not a random coil; it is an autonomous folding unit, and the portion corresponding to insulin is identical with insulin in terms of conformational stability.
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