The crystal structure of human interferon β at 2.2-Å resolution

Karpusas, Michael; Nolte, Matthias; Benton, Christopher B.; Meier, Werner; Lipscomb, William N.; Goelz, Susan

doi:10.1073/pnas.94.22.11813

Cited by 196 publications

(137 citation statements)

References 44 publications

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“…These predictions have been confirmed on the recently solved, three-dimensional structure of the human IFN-␤1a (37). The likelihood that Tyr 125 is a buried residue, involved in intramolecular bonds, was confirmed on the three-dimensional structure of human IFN-␤1a (37).…”

Section: Design Of Ifn-␤ Mutants-supporting

confidence: 64%

Differences in Activity between α and β Type I Interferons Explored by Mutational Analysis

Runkel¹,

Pfeffer²,

Lewerenz³

et al. 1998

Journal of Biological Chemistry

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Type I interferon (IFN) subtypes ␣ and ␤ share a common multicomponent, cell surface receptor and elicit a similar range of biological responses, including antiviral, antiproliferative, and immunomodulatory activities. However, ␣ and ␤ IFNs exhibit key differences in several biological properties. For example, IFN-␤, but not IFN-␣, induces the association of tyrosine-phosphorylated receptor components ifnar1 and ifnar2, and has activity in cells lacking the IFN receptor-associated, Janus kinase tyk2. To define the structural basis for these functional differences we produced human IFN-␤ with point mutations and compared them to wild-type IFN-␤ in assays that distinguish ␣ and ␤ IFN subtypes. IFN-␤ mutants with charged residues (N86K, N86E, or Y92D) introduced at two positions in the C helix lost the ability to induce the association of tyrosine-phosphorylated receptor chains and had reduced activity on tyk2-deficient cells. The combination of negatively charged residues N86E and Y92D (homologous with IFN-␣8) increased the cross-species activity of the mutant IFN-␤s on bovine cells to a level comparable to that of human IFN-␣s. In contrast, point mutations in the AB loop and D helix had no significant effect on these subtypespecific activities. A subset of these latter mutations did, however, reduce activity in a manner analogous to IFN-␣ mutations. The effects of these mutations on IFN-␤ activity are discussed in the context of a family of related ligands acting through a common receptor and signaling pathway.The mammalian type I IFNs, 1 produced in response to viral infection and other inducers, are divided into ␣ and ␤ subtypes on the basis of their reactivity with antisera raised against IFNs derived, respectively, from leukocytes and fibroblasts (1). The human IFN-␣s are encoded by a family of at least 15 different genes, while IFN-␤ is the unique member of its subtype (2). Primary sequence comparison between the ␣ and ␤ subtypes reveal an approximately 50% amino acid homology, while the amino acid homologies between the IFN-␣ subtypes are approximately 80% (2, 3), reinforcing the division between IFN-␣ and -␤ subtypes.As the pleiotropic nature of these cytokines became apparent, with both subtypes eliciting a similar range of biological activities (3), differences between ␣ subtypes, and between IFN-␣ and -␤s, in potency and cell type specific activities were noted (4). In particular, IFN-␤ elicits a markedly higher antiproliferation response in some cell types such as (5), embryonal carcinoma, melanoma and melanocytes than do IFN-␣s (6, 7, and references therein). Higher potency of IFN-␤ in treatment of multiple sclerosis and certain cancers has been observed (7).The entire class of type I IFNs elicit their biological activities through engagement of a common cell surface receptor (8 -10). Two chains of the receptor, ifnar1 and ifnar2, both members of the type two cytokine receptor family, have been identified (11-15). Both components are necessary for function and in the absence of either there is neither...

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Section: Design Of Ifn-␤ Mutants-supporting

confidence: 64%

Differences in Activity between α and β Type I Interferons Explored by Mutational Analysis

Runkel¹,

Pfeffer²,

Lewerenz³

et al. 1998

Journal of Biological Chemistry

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“…Type I IFNs belong to the class of helical cytokines (6) and are built by five helices. The structure of several type I IFNs have been resolved, such as murine IFN␤ (7), human IFN␣2 (8,9), human IFN␤ (10), and ovine IFN (11). Mutational studies have revealed functionally important residues on IFNs (reviewed in Ref.…”

Section: Type I Interferons (Ifn)mentioning

confidence: 99%

New Structural and Functional Aspects of the Type I Interferon-Receptor Interaction Revealed by Comprehensive Mutational Analysis of the Binding Interface

Piehler¹,

Roisman

Schreiber

2000

Journal of Biological Chemistry

140

163

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Type I interferons bind to two cell surface receptors, ifnar1 and ifnar2, as the first step in the activation of several signal transduction pathways that elicit an antiviral state and an anti-proliferative response. Here, we quantitatively mapped the complete binding region of ifnar2 on interferon (IFN)␣2 by 35 individual mutations to alanine and isosteric residues. Of the six "hot-spot" residues identified (Leu-30, Arg-33, Arg-144, Ala-145, Met-148, and Arg-149), four are located on the E-helix, which is located at the center of the binding site flanked by residues on the A-helix and the AB-loop. The contribution of residues of the D-helix, which have been previously implicated in binding, proved to be marginal for the interaction with the extracellular domain of ifnar2. Interestingly, the ifnar2 binding site overlaps the largest continuous hydrophobic patch on IFN␣2. Thus, hydrophobic interactions seem to play a significant role stabilizing this interaction, with the charged residues contributing toward the rapid association of the complex. Relating the anti-viral and anti-proliferative activity of the various interferon mutants with their affinity toward ifnar2 results in linear function over the whole range of affinities investigated, suggesting that ifnar2 binding is the rate-determining step in cellular activation. Dose-time analysis of the anti-viral response revealed that shortening the incubation time of low-level activation cannot be compensated by higher IFN doses. Considering the strict dependence of the cellular response on affinity, these results suggest that for maintaining transcription of IFN-responsive genes over a longer time period, low but continuous signaling through the IFN receptor is essential. Type I interferons (IFN)1 are a family of homologous cytokines, which potently elicit an anti-viral and anti-proliferative state in cells. All human type I IFNs (IFN␣, ␤, , and ) bind to a cell surface receptor consisting of two transmembrane proteins, ifnar1 (1) and ifnar2 (2), which associate upon binding. Binding of IFN to its receptor mediates activation of numerous genes (3) through different signal transduction pathways (reviewed in Ref. 4). Intriguingly, different expression profiles are induced by different IFNs, apparently through the same receptor, with particular differences between IFN␣ and IFN␤ (3, 5). However, the molecular mechanisms underlying the functional differences between IFNs are still unknown. Type I IFNs belong to the class of helical cytokines (6) and are built by five helices. The structure of several type I IFNs have been resolved, such as murine IFN␤ (7), human IFN␣2 (8, 9), human IFN␤ (10), and ovine IFN (11). Mutational studies have revealed functionally important residues on IFNs (reviewed in Ref. 12), which can be ascribed to distinct functional epitopes that interact with ifnar1 and ifnar2 (13, 14). The binding site for ifnar2 was mainly mapped on the AB-loop and D-helix and the binding site for ifnar1 on the C-helix. However, comparison with homologous cytokines...

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“…Type I IFNs belong to the class of helical cytokines and are built of five helices. The structures of human IFN-␣2 (3) and IFN-␤ have been resolved (4). The receptor structures are unknown, but can be modeled by homology to human cytokine receptors with known structures such as tissue factor (5) and IFN-␥ receptor (6).…”

mentioning

confidence: 99%

Structure of the interferon-receptor complex determined by distance constraints from double-mutant cycles and flexible docking

Roisman

Piehler

Trosset

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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The pleiotropic activity of type I interferons has been attributed to the specific interaction of IFN with the cell-surface receptor components ifnar1 and ifnar2. To date, the structure of IFN has been solved, but not that of the receptor or the complex. In this study, the structure of the IFN-␣2-ifnar2 complex was generated with a docking procedure, using nuclear Overhauser effect-like distance constraints obtained from double-mutant cycle experiments. The interaction free energy between 13 residues of the ligand and 11 of the receptor was measured by double-mutant cycles. Of the 100 pairwise interactions probed, five pairs of residues were found to interact. These five interactions were incorporated as distance constraints into the flexible docking program PRODOCK by using fixed and movable energy-gradient grids attached to the receptor and ligand, respectively. Multistart minimization and Monte Carlo minimization docking of IFN-␣2 onto ifnar2 converged to a welldefined average structure, with the five distance constraints being satisfied. Furthermore, no structural artifacts or intraloop energy strain were observed. The mutual binding sites on IFN-␣2 and ifnar2 predicted from the model showed an almost complete superposition with the ones determined from mutagenesis studies. Based on this structure, differences in IFN-␣2 versus IFN-␤ binding are discussed.protein-protein interaction ͉ PRODOCK ͉ Monte Carlo minimization ͉ grids T ype I interferons (IFNs) are a family of homologous cytokines that potently elicit an antiviral and antiproliferative state in cells. All human type I IFNs (IFN-␣, -␤, and -) bind to a cell surface receptor consisting of two transmembrane proteins, type I IFN receptor (ifnar) 1 (1) and ifnar2 (2), which associate upon binding. IFN binds with high affinity to ifnar2, probably recruiting ifnar1 subsequently. Type I IFNs belong to the class of helical cytokines and are built of five helices. The structures of human IFN-␣2 (3) and IFN-␤ have been resolved (4). The receptor structures are unknown, but can be modeled by homology to human cytokine receptors with known structures such as tissue factor (5) and IFN-␥ receptor (6). Mutational studies have revealed the mutual binding sites on IFN-␣2 and ifnar2. On IFN-␣2, ifnar2 binds to the A helix (residues 12-15), the AB loop (residues 26-35), and the E helix (residues 144-153) (7), whereas on ifnar2, IFN-␣2 binds to three loops of the N-terminal domain of the receptor (residues 45-52, 75-82, and 102-106) with no significant binding detected toward the Cterminal domain (8-10). Determination of the receptor-ligand structure will significantly promote our understanding of IFN signaling at the molecular level.Docking of protein complexes, and calculating the conformational changes that occur at the binding interface, is a computational challenge. Rigid protein docking software algorithms are fast and can be used to dock two proteins for which the NMR or x-ray structures have been solved independently (11, 12). However, successful docking relies o...

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The crystal structure of human interferon β at 2.2-Å resolution

Cited by 196 publications

References 44 publications

Differences in Activity between α and β Type I Interferons Explored by Mutational Analysis

Differences in Activity between α and β Type I Interferons Explored by Mutational Analysis

New Structural and Functional Aspects of the Type I Interferon-Receptor Interaction Revealed by Comprehensive Mutational Analysis of the Binding Interface

Structure of the interferon-receptor complex determined by distance constraints from double-mutant cycles and flexible docking

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