Recognition of granulocyte-macrophage colony-stimulating factor by specific S100 proteins.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic myelopoietic growth factor and proinflammatory cytokine, clinically used for multiple indications and serving as a promising target for treatment of many disorders, including cancer, multiple sclerosis, rheumatoid arthritis, psoriasis, asthma, COVID-19. We have previously shown that dimeric Ca-bound forms of S100A6 and S100P proteins, members of the multifunctional S100 protein family, are specific to GM-CSF. To probe selectivity of these interactions, the affinity of recombinant human GM-CSF to dimeric Ca-loaded forms of 18 recombinant human S100 proteins was studied by surface plasmon resonance spectroscopy.

The active site of the SGNH hydrolase-like fold proteins: Nucleophile-oxyanion (Nuc-Oxy) and Acid-Base zones.

SGNH hydrolase-like fold proteins are serine proteases with the default Asp-His-Ser catalytic triad. Here, we show that these proteins share two unique conserved structural organizations around the active site: (1) the Nuc-Oxy Zone around the catalytic nucleophile and the oxyanion hole, and (2) the Acid-Base Zone around the catalytic acid and base. The Nuc-Oxy Zone consists of 14 amino acids cross-linked with eight conserved intra- and inter-block hydrogen bonds.

Interaction of S100A6 Protein with the Four-Helical Cytokines.

S100 is a family of over 20 structurally homologous, but functionally diverse regulatory (calcium/zinc)-binding proteins of vertebrates. The involvement of S100 proteins in numerous vital (patho)physiological processes is mediated by their interaction with various (intra/extra)cellular protein partners, including cell surface receptors. Furthermore, recent studies have revealed the ability of specific S100 proteins to modulate cell signaling via direct interaction with cytokines.

Kinetics of Ca Dissociation from Cod Parvalbumin Studied by Fluorescent Stopped-flow Method.

Background: Small Ca-binding protein parvalbumin possesses two strong Ca/Mg- binding sites located within two EF-hand domains. Most parvalbumins have no tryptophan residues, while cod protein contains a single tryptophan residue, which fluorescence (spectrum maximum position and fluorescence quantum yield) is highly sensitive to the Ca association/dissociation.

Objective: Intrinsic protein fluorescence of cod parvalbumin can be used for elucidating the mechanism of Ca binding to this protein.

Specific S100 Proteins Bind Tumor Necrosis Factor and Inhibit Its Activity.

Tumor necrosis factor (TNF) inhibitors (anti-TNFs) represent a cornerstone of the treatment of various immune-mediated inflammatory diseases and are among the most commercially successful therapeutic agents. Knowledge of TNF binding partners is critical for identification of the factors able to affect clinical efficacy of the anti-TNFs. Here, we report that among eighteen representatives of the multifunctional S100 protein family, only S100A11, S100A12 and S100A13 interact with the soluble form of TNF (sTNF) in vitro.

Calcium-Bound S100P Protein Is a Promiscuous Binding Partner of the Four-Helical Cytokines.

S100 proteins are multifunctional calcium-binding proteins of vertebrates that act intracellularly, extracellularly, or both, and are engaged in the progression of many socially significant diseases. Their extracellular action is typically mediated by the recognition of specific receptor proteins. Recent studies indicate the ability of some S100 proteins to affect cytokine signaling through direct interaction with cytokines.

Canonical structural-binding modes in the calmodulin-target protein complexes.

Intracellular calcium sensor protein calmodulin (CaM) belongs to the large EF-hand protein superfamily. CaM shows a unique and not fully understood ability to bind to multiple targets, allows them to participate in a variety of regulatory processes. The protein has two approximately symmetrical globular domains (the N- and C-lobes).

What Is Parvalbumin for?

Parvalbumin (PA) is a small, acidic, mostly cytosolic Ca-binding protein of the EF-hand superfamily. Structural and physical properties of PA are well studied but recently two highly conserved structural motifs consisting of three amino acids each (clusters I and II), which contribute to the hydrophobic core of the EF-hand domains, have been revealed. Despite several decades of studies, physiological functions of PA are still poorly known.

Interferon-β Activity Is Affected by S100B Protein.

Interferon-β (IFN-β) is a pleiotropic cytokine secreted in response to various pathological conditions and is clinically used for therapy of multiple sclerosis. Its application for treatment of cancer, infections and pulmonary diseases is limited by incomplete understanding of regulatory mechanisms of its functioning. Recently, we reported that IFN-β activity is affected by interactions with S100A1, S100A4, S100A6, and S100P proteins, which are members of the S100 protein family of multifunctional Ca-binding proteins possessing cytokine-like activities (Int J Mol Sci.

Erythropoietin Interacts with Specific S100 Proteins.

Erythropoietin (EPO) is a clinically significant four-helical cytokine, exhibiting erythropoietic, cytoprotective, immunomodulatory, and cancer-promoting activities. Despite vast knowledge on its signaling pathways and physiological effects, extracellular factors regulating EPO activity remain underexplored. Here we show by surface plasmon resonance spectroscopy, that among eighteen members of Ca-binding proteins of the S100 protein family studied, only S100A2, S100A6 and S100P proteins specifically recognize EPO with equilibrium dissociation constants ranging from 81 nM to 0.

Specific cytokines of interleukin-6 family interact with S100 proteins.

Cytokines of interleukin-6 (IL-6) family are important signaling proteins involved in various physiological and pathological processes. Earlier, we described interactions between IL-11 and S100P/B proteins from the family of S100 proteins engaged in the pathogenesis of numerous diseases. We probed here interactions between seven IL-6 family cytokines (IL-6, IL-11, OSM, LIF, CNTF, CT-1, and CLCF1) and fourteen S100 proteins (S100A1/A4/A6/A7/A8/A9/A10/A11/A12/A13/A14/A15/B/P).

Ca/Sr Selectivity in Calcium-Sensing Receptor (CaSR): Implications for Strontium's Anti-Osteoporosis Effect.

The extracellular calcium-sensing receptor (CaSR) controls vital bone cell functions such as cell growth, differentiation and apoptosis. The binding of the native agonist (Ca) to CaSR activates the receptor, which undergoes structural changes that trigger a cascade of events along the cellular signaling pathways. Strontium (in the form of soluble salts) has been found to also be a CaSR agonist.

Structural and functional significance of the amino acid differences ValThr, SerAla, AsnSer, and AlaSer in 3C-like proteinases from SARS-CoV-2 and SARS-CoV.

Three dimensional structures of (chymo)trypsin-like proteinase (3CL) from SARS-CoV-2 and SARS-CoV differ at 8 positions. We previously found that the ValLeu, LysArg, PheHis, and AsnLys mutations in these enzymes can change the orientation of the N- and C-terminal domains of 3CL relative to each other, which leads to a change in catalytic activity. This conclusion was derived from the comparison of the structural catalytic core in 169 (chymo)trypsin-like proteinases with the serine/cysteine fold.

Strontium Binding to α-Parvalbumin, a Canonical Calcium-Binding Protein of the "EF-Hand" Family.

Strontium salts are used for treatment of osteoporosis and bone cancer, but their impact on calcium-mediated physiological processes remains obscure. To explore Sr interference with Ca binding to proteins of the EF-hand family, we studied Sr/Ca interaction with a canonical EF-hand protein, α-parvalbumin (α-PA). Evaluation of the equilibrium metal association constants for the active Ca binding sites of recombinant human α-PA ('CD' and 'EF' sites) from fluorimetric titration experiments and isothermal titration calorimetry data gave 4 × 10 M and 4 × 10 M for Ca, and 2 × 10 M and 2 × 10 M for Sr.

Structural leitmotif and functional variations of the structural catalytic core in (chymo)trypsin-like serine/cysteine fold proteinases.

Proteinases with the (chymo)trypsin-like serine/cysteine fold comprise a large superfamily performing their function through the Acid - Base - Nucleophile catalytic triad. In our previous work (Denesyuk AI, Johnson MS, Salo-Ahen OMH, Uversky VN, Denessiouk K. Int J Biol Macromol.

The Highly Conservative Cysteine of Oncomodulin as a Feasible Redox Sensor.

Oncomodulin (Ocm), or parvalbumin β, is an 11-12 kDa Ca-binding protein found inside and outside of vertebrate cells, which regulates numerous processes via poorly understood mechanisms. Ocm consists of two active Ca-specific domains of the EF-hand type ("helix-loop-helix" motif), covered by an EF-hand domain with inactive EF-hand loop, which contains a highly conservative cysteine with unknown function. In this study, we have explored peculiarities of the microenvironment of the conservative Cys18 of recombinant rat Ocm (rWT Ocm), redox properties of this residue, and structural/functional sensitivity of rWT Ocm to the homologous C18S substitution.

Interferon Beta Activity Is Modulated via Binding of Specific S100 Proteins.

Interferon-β (IFN-β) is a pleiotropic cytokine used for therapy of multiple sclerosis, which is also effective in suppression of viral and bacterial infections and cancer. Recently, we reported a highly specific interaction between IFN-β and S100P lowering IFN-β cytotoxicity to cancer cells (Int J Biol Macromol. 2020; 143: 633-639).

Papain-like cysteine proteinase zone (PCP-zone) and PCP structural catalytic core (PCP-SCC) of enzymes with cysteine proteinase fold.

There are several families of cysteine proteinases with different folds - for example the (chymo)trypsin fold family and papain-like fold family - but in both families the hydrolase activity of cysteine proteinases requires a cysteine residue as the catalytic nucleophile. In this work, we have analyzed the topology of the active site regions in 146 three-dimensional structures of proteins belonging to the Papain-like Cysteine Proteinase (PCP) superfamily, which includes papain as a typical representative of this protein superfamily. All analyzed enzymes contain a unique structurally closed conformation - a "PCP-Zone" - which can be divided into two groups, Class A and Class B.

α-Lactalbumin, Amazing Calcium-Binding Protein.

α-Lactalbumin (α-LA) is a small (Mr 14,200), acidic (pI 4-5), Ca-binding protein. α-LA is a regulatory component of lactose synthase enzyme system functioning in the lactating mammary gland. The protein possesses a single strong Ca-binding site, which can also bind Mg, Mn, Na, K, and some other metal cations.

System Approach for Building of Calcium-Binding Sites in Proteins.

We introduce five new local metal cation (first of all, Ca) recognition units in proteins: Clamp, Clamp, Clamp, Clamp and Clamp. In these units, the backbone oxygen atom of a residue in position "n" of an amino acid sequence and side-chain oxygen atom of a residue in position "n + i" (i = -2 to +2) directly interact with a metal cation. An analysis of the known "Ca-bound niches" in proteins has shown that a system approach based on the simultaneous use of the Clamp units and earlier proposed One-Residue (OR)/Three-Residue (TR) units significantly improves the results of constructing metal cation-binding sites in proteins.

Mouse S100G protein exhibits properties characteristic of a calcium sensor.

Bovine S100 G (calbindin D, small Ca-binding protein of the EF-hand superfamily) is considered as a calcium buffer protein; i.e., the binding of Ca practically does not change its general conformation.

Highly specific interaction of monomeric S100P protein with interferon beta.

S100 proteins are EF-hand calcium-binding proteins of vertebrates exerting numerous intra- and extracellular actions and involved into multiple diseases. Some of S100 proteins serve as extracellular damage signals via interaction with receptors. Although several S100 proteins directly bind specific cytokines, this phenomenon remains underexplored.

Experimental Insight into the Structural and Functional Roles of the 'Black' and 'Gray' Clusters in Recoverin, a Calcium Binding Protein with Four EF-Hand Motifs.

Recently, we have found that calcium binding proteins of the EF-hand superfamily (i.e., a large family of proteins containing helix-loop-helix calcium binding motif or EF-hand) contain two types of conserved clusters called cluster I ('black' cluster) and cluster II ('grey' cluster), which provide a supporting scaffold for the Ca binding loops and contribute to the hydrophobic core of the EF-hand domains.

Monomeric state of S100P protein: Experimental and molecular dynamics study.

S100 proteins constitute a large subfamily of the EF-hand superfamily of calcium binding proteins. They possess one classical EF-hand Ca-binding domain and an atypical EF-hand domain. Most of the S100 proteins form stable symmetric homodimers.

Analyzing the structural and functional roles of residues from the 'black' and 'gray' clusters of human S100P protein.

Two highly conserved structural motifs observed in members of the EF-hand family of calcium binding proteins. The motifs provide a supporting scaffold for the Ca2+ binding loops and contribute to the hydrophobic core of the EF-hand domain. Each structural motif represents a cluster of three amino acids called cluster I ('black' cluster) and cluster II ('grey' cluster).