Biomedical subjects

Ferenc Hudecz

Publications and source records attributed to Ferenc Hudecz.

At least 37 records · Page 2Linked to original sources

PubMed2004

Modeling of main characteristics of bullous pemphigoid antigen-2 (BPAG2) peptide structure in serological recognition by autoantibodies.

The serum level of autoantibodies against autoantigens of the bullous pemphigoid peptides 1 and 2 (BPAG1 and BPAG2) is a relevant diagnostic marker. Twelve representative sera of BP were tested against the RSILPYGDSMDRIEKDRLQMAP amino acid sequence that is an epitope fragment of the NC16A domain of BPAG2 (AC Q02802; 507-528) to find the most suitable antigenic form for specific detection of autoantibodies of BP patients' sera by quantitative ELISA system. The antigenic epitope sequence was presented as an antigen in a carrier free form of dimeric peptide (BP22), dimeric peptide fused to glutathione S-transferase (GST-BP22) or dimeric peptide chemically conjugated to polyLys(Ser-DL-Alam) (SAK-BP22). The intensity of ELISA reaction was highest against the recombinant fusion antigen GSTBP22; the chemically conjugated SAK-BP22 performed less well than the free dimeric form of the peptide. In the case of the GST-BP22 antigen, the (GST-BP22)-(GST)492nm optical density values were determined. There was no significant difference between the mean ODs of the GST-BP22 and the SAK-BP22 (0.888 vs. 0.892, p= 0.9726). Conjugating the epitope peptide with the synthetic carrier SAK was advantageous, as it abrogated cross-reactivity with GST carrier protein. Consequently, the SAKBP22 conjugate appears to be the most reliable assay component, avoiding cross-reactivity with GST and simplifying the detection and evaluation of BP autoantibodies in routine ELISA diagnostic system.

Autoantibodies↗

PubMed2004

On the sequential determinants of calpain cleavage.

The structural clues of substrate recognition by calpain are incompletely understood. In this study, 106 cleavage sites in substrate proteins compiled from the literature have been analyzed to dissect the signal for calpain cleavage and also to enable the design of an ideal calpain substrate and interfere with calpain action via site-directed mutagenesis. In general, our data underline the importance of the primary structure of the substrate around the scissile bond in the recognition process. Significant amino acid preferences were found to extend over 11 residues around the scissile bond, from P(4) to P(7)'. In compliance with earlier data, preferred residues in the P(2) position are Leu, Thr, and Val, and in P(1) Lys, Tyr, and Arg. In position P(1) ', small hydrophilic residues, Ser and to a lesser extent Thr and Ala, occur most often. Pro dominates the region flanking the P(2)-P(1)' segment, i.e. positions P(3) and P(2)'-P(4)'; most notable is its occurrence 5.59 times above chance in P(3)'. Intriguingly, the segment C-terminal to the cleavage site resembles the consensus inhibitory region of calpastatin, the specific inhibitor of the enzyme. Further, the position of the scissile bond correlates with certain sequential attributes, such as secondary structure and PEST score, which, along with the amino acid preferences, suggests that calpain cleaves within rather disordered segments of proteins. The amino acid preferences were confirmed by site-directed mutagenesis of the autolysis sites of Drosophila calpain B; when amino acids at key positions were changed to less preferred ones, autolytic cleavage shifted to other, adjacent sites. Based on these preferences, a new fluorogenic calpain substrate, DABCYLTPLKSPPPSPR-EDANS, was designed and synthesized. In the case of micro- and m-calpain, this substrate is kinetically superior to commercially available ones, and it can be used for the in vivo assessment of the activity of these ubiquitous mammalian calpains.

Amino Acid Sequence↗

PubMed2004

In vitro T-cell immunogenicity of oligopeptides derived from the region 92-110 of the 16-kDa protein of Mycobacterium tuberculosis.

The 16-kDa protein of Mycobacterium tuberculosis provokes specific immune responses; it is thus a target for the development of peptide-based diagnostic reagents and subunit vaccines. Previous studies have demonstrated the presence of several regions containing murine and human T-cell epitopes. Within the 91-110 immunodominant domain, we found that peptides comprising the sequence of 91SEFAYGSFVRTVSL104 elicit specific T-cell responses in both human T-cell clones and human peripheral blood mononuclear cells (PBMC) from PPD+ (purified protein derivative) individuals. Elongation of this peptide towards the C-terminal end did not provide more effective peptides, but the removal of residue 91Ser resulted in an almost complete loss of functionality. However, the introduction of an acetyl group at the N-terminal of residue 92Glu produced a shorter peptide (Ac-92EFAYGSFVRTVSL104) exhibiting properties required for efficient T-cell responses. CD measurements indicated that peptide 91SEFAYGSFVRTVSLPVGADE110 adopts a helical conformation in trifluoroethanol. We found that the N-terminal part of this sequence plays a major role in the induction of proliferative T-cell responses and is responsible for the highly ordered, helical secondary structure. The "lead" structure described here could also be considered in the development of synthetic peptides or multicomponent peptide mixtures for the early detection, monitoring, or preventing Mycobacterium tuberculosis infection with optimized T-cell response-provoking capacity.

Amino Acid Sequence↗

PubMed2004

Polypeptide conjugates comprising a beta-amyloid plaque-specific epitope as new vaccine structures against Alzheimer's disease.

Immunotherapeutic approaches designed to induce a humoral immune response have recently been developed for possible vaccination to the treatment of Alzheimer's disease (AD). Based on the identification of Abeta(4-10) (FRHDSGY) as the predominant B-cell epitope recognized by therapeutically active antisera from transgenic AD mice, branched polypeptide conjugates with this epitope peptide were synthesized and characterized. In order to produce immunogenic constructs, the Abeta(4-10) epitope alone or together with a promiscuous T-helper cell epitope peptide (FFLLTRILTIPQSLD) were attached via thioether linkage to different branched chain polymeric polypeptides with Ser or Glu in the side chains. A single peptide containing both an Abeta(4-10) and T-helper cell epitope, joined by a dipeptide Cys-Acp spacer, was also attached through the thiol function to chloroacetylated poly[Lys(Seri-DL-Alax)] (SAK). Comparative binding studies of the conjugates with a monoclonal antibody against the beta-amyloid(1-17) peptide in mice were performed by direct ELISA. The conformational preferences of carriers and conjugates in water and in a 9:1 trifluoroethanol:water mixture (v/v) was analyzed by CD spectroscopy. Experimental data showed that the chemical nature of the carrier macromolecule, and the attachment site of the epitope to the carrier, have significant effects on antibody recognition, but have no marked influence on the solution conformation of the conjugates.

Alzheimer Disease↗

PubMed2004

Functional mapping of the Fc gamma RII binding site on human IgG1 by synthetic peptides.

Receptors specific for the Fc part of IgG (Fc gamma R) are expressed by several cell types and play diverse roles in immune responses. Impaired function of the activating and inhibitory Fc gamma R may result in autoimmunity. Thus, the modulation of IgG-Fc gamma R interaction can be a target for the development of treatments for some autoimmune and inflammatory diseases. This study addresses the localization and functional characterization of linear sequences in human IgG1 which bind to Fc gamma RII. Peptides with overlapping sequences derived from the CH2 domain of human IgG1 between P(234) and S(298) were synthesized and used in binding and functional experiments. Binding of the peptides to Fc gamma R was assayed in vitro and ex vivo, and peptides found to interact were functionally tested. The shortest effective peptide was T(256)-P(271), which bound to soluble recombinant Fc gamma RIIb with K(d)=6 x 10(6) M(-1). The biotinylated peptides R(255)-P(271) and T(256)-P(271) complexed by avidin exhibited functional activity; they induced Fc gamma RIIb-mediated inhibition of the BCR-triggered Ca(2+) response of human Burkitt lymphoma cells, and inflammatory cytokine production (TNF-alpha and IL-6) by the human monocyte cell line MonoMac. In conclusion, our results suggest that the selected peptides functionally represent the Fc gamma RII-binding part of IgG1.

Binding Sites↗

PubMed2004

Heteroclitic recognition of combinatorial TX1TX2T peptide mixtures by mucin-2 protein specific monoclonal antibody.

The mucin-2 (MUC2) glycoprotein secreted by the epithelial cells of human colon may be abnormally under-glycosylated in the case of cancer. Monoclonal antibody (mAb) 994 raised against the immunogenic part of the protein core, recognizes malignant human colon tissues as well as pentapeptides with TX1TX2T motif present in MUC2. Using a combinatorial approach and ELISA experiments it was found that mAb 994 is able to recognize peptides of the sub-library TQTX2T very strongly, and to some extent also peptides from TETX2T, TLTX2T and TVTX2T sub-libraries. Binding studies with peptides corresponding to the TQTX2T and TETX2T sub-libraries showed that mAb 994 recognized only six peptides (IC50 = 9-208 micromol dm(-3)) from the 19 compounds of the TQTX2T sub-library and only three peptides (IC50 = 3500-16700 micromol dm(-3)) from the 'second-best' TETX2T sub-library. The most pronounced mAb binding occurred when Gln was in position X1 and it was much weaker in the case of Glu, Val or Leu. As for X2 amino acids, the presence of Pro, Ala can provide a strong, while Tyr, Trp, Phe and Ser a weaker, peptide-antibody interaction. Data from this study suggest that pentapeptide TQTPT, whose sequence is present in the native protein, is bound most strongly. However, almost identical binding properties were observed with peptide TQTAT, whose sequence is not present in the protein. Apart from this, some other 'heteroclitic' peptides were found with a different rank in the binding-hierarchy. Based on these peptides artificial compounds can be prepared as potential candidates for vaccine development. Results of this study also provide a rationale for understanding the molecular background of the heteroclitic nature of the MUC2 protein core specific mAb 994.

Amino Acid Sequence↗

PubMed2004

Synthesis and structural characterization of bioactive peptide conjugates using thioether linkage approaches.

Applications of cysteine-insertion and thioether linkage approaches to the preparation of a number of bioactive peptide conjugates are reported. Peptides containing epitopes from (i) herpes simplex virus type 1 glycoprotein D, (ii) a specific N-terminal beta-amyloid epitope recognized by therapeutically active antibodies, and (iii) a GnRH-III peptide from sea lamprey with antitumour activity, were elongated with Cys residues and attached to a chloroacetylated tetratuftsin derivative carrier via a thioether linkage either directly, or by insertion of a spacer. The structures and molecular homogeneity of all the peptide conjugates were ascertained by HPLC, MALDI and electrospray mass spectrometry. The use of a spacer such as an oligoglycine or GFLG-tetrapeptide gave an increased yield in the conjugation reaction and enhanced reaction rates. In the formation of cysteinyl-thioether linkages, it was found that the position of flanking Cys residues markedly influenced the conjugation reaction and the formation of intermolecular epitope disulfide-dimers. C-terminal Cys residues gave thioether conjugates with significantly diminished epitope-dimerization, while Cys at the N-terminal caused rapid disulfide-dimerization, thereby preventing efficient conjugation.

Acetates↗

PubMed2004

Natively unfolded tubulin polymerization promoting protein TPPP/p25 is a common marker of alpha-synucleinopathies.

The novel basic, heat-stable tubulin polymerization promoting protein TPPP/p25 is associated with microtubules in vitro and can induce the formation of aberrant microtubule assemblies. We show by 1H-NMR spectroscopy that TPPP/p25 is natively unfolded. Antisera against peptide 186GKGKAGRVDLVDESG200NH2 (186-200) are highly specific to TPPP/p25. Immunohistochemistry and confocal microscopy demonstrates that TPPP/p25 is enriched in filamentous alpha-synuclein bearing Lewy bodies of Parkinson's (PD) and diffuse Lewy body disease (DLBD), as well as glial inclusions of multiple system atrophy (MSA). There is a correlation between TPPP/p25 and alpha-synuclein immunoreactivity in Western blot. In contrast, TPPP/p25 is not associated with abnormally phosphorylated tau in various inclusions of Pick's disease (PiD), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). However, electron microscopy confirms clusters of TPPP/p25 immunoreactivity along filaments of unstructured but not compact neurofibrillary tangles in Alzheimer's disease (AD). TPPP/p25 seems to be a novel marker of alpha-synucleinopathies.

Aged↗

PubMed2003

Synthesis, solution structure analysis and antibody binding of cyclic epitope peptides from glycoprotein D of Herpes simplex virus type I.

Two cyclic peptides with a thioether bond have been synthesised corresponding to the 9-22 (9LKMADPNRFRGKDL(22)) sequence of glycoprotein D (gD-1) of Herpes simplex virus. The role of the secondary structure in protein-specific monoclonal antibody recognition was investigated. The sequence selected for this study comprises a strongly antigenic site adopting a beta-turn at residues 14Pro-(15)Asn. Thioether bond was formed between the free thiol group of cysteine or homocysteine inserted in position 11 and the chloroacetylated side chain of lysine in position 18. We report here the preparation of cyclic peptides containing Cys or Hcy in position 11, differing only in one methylene group. The linear precursor peptides were synthesised by Boc/Bzl strategy on MBHA resin, and the cyclisation was carried out in alkaline solution. The secondary structure of the peptides was studied by CD, FT-IR and NMR spectroscopy. The CD and FT-IR data have revealed fundamental changes in the solution conformation of the two compounds. The CH(2) group difference significantly resulted in the altered turn structure at the 12Ala and 13Asp as identified by NMR spectroscopy. The antibody binding properties of the cyclopeptides studied by gD-specific monoclonal antibody (A16) in direct and competition enzyme-linked immunosorbent assay (ELISA) were also not the same. We found that peptide LK[HcyADPNRFK]GKDL exhibited higher affinity to Mab A16 than peptide LK[CADPNRFK]GKDL, however, their reactivity was significantly lower compared to the linear ones. Our results clearly show the importance of secondary structure in an antibody binding and demonstrate that even a slight modification of the primary structure dramatically could influence the immune recognition of the synthetic antigens.

Amino Acid Sequence↗

PubMed2003

Differential recognition of altered peptide ligands distinguishes two functionally discordant (arthritogenic and nonarthritogenic) autoreactive T cell hybridoma clones.

Intravenous injection of a cartilage proteoglycan (aggrecan)-specific Th1 hybridoma clone 5/4E8 induced joint lesions similar to those seen in either primary or adoptively transferred arthritis in BALB/c mice. A sister clone, TA20, recognizing the same peptide epitope of human aggrecan and using the same Vbeta4 and Valpha1 segments, failed to induce joint inflammation. This study examines the fine epitope specificities of these two clones. Both 5/4E8 and TA20 hybridomas were generated using T cells from the same arthritic animal that has been immunized with human aggrecan, and both clones recognized peptides containing a consensus GRVRVNSAY sequence. However, flanking regions outside this nonapeptide sequence region had differential impact on peptide recognition by the two clones. Similarly, when single amino acid substitutions were introduced to the consensus sequence, significant differences were detected in the epitope recognition patterns of the T cell hybridomas. The 5/4E8 hybridoma showed greater flexibility in recognition, including a higher responsiveness to the corresponding self (mouse) aggrecan peptide, and produced more inflammatory cytokines (IFN-gamma and TNF-alpha), whereas hybridoma TA20 produced IL-5 in response to either human or mouse self peptide stimulation. These results demonstrate that, within the pool of immunodominant (foreign) peptide-activated lymphocytes, marked individual differences of degeneracy exist in T cell recognition, with possible implications to autopathogenic T cell functions.

Aggrecans↗

PubMed2003

Isomer-dependent daunomycin release and in vitro antitumour effect of cis-aconityl-daunomycin.

Two isomers of cis-aconytil-daunomycin (cAD) were isolated after the reaction of daunomycin with cis-aconitic-anhydride. The structure of the isomers was identified by MS-spectroscopy and 1H and 13C NMR experiments. In contrast with the assumptions described earlier, our results show that the two isomers belong to the cis- and trans-isomers of the alpha-monoamide of cis-aconityl-daunomycin, respectively. We found that the pH dependent daunomycin release is different for the two isomers. Comparative analysis of the in vitro antitumour effect of the isomers on c26 colon carcinoma and on MDA-MB 435P human breast carcinoma cell lines showed that cAD-1 is more potent than cAD-2, but the extent of differences is tumour cell dependent. The results of this study might be appreciated in the light of the use of acid-labile spacer for the design and preparation of protein/peptide conjugates of drugs by indicating that isomers could possess markedly different biological activity.

Antineoplastic Agents↗

PubMed2003

Identification and solution conformation of multiple epitopes recognized by a MUC2 mucin-specific monoclonal antibody.

We have identified the optimal epitope, 21TQTPT25, in the tandem repeat of mucin 2 (MUC2) glycoprotein by using glycoprotein-specific monoclonal antibody, MAb 994, and synthetic, overlapping and truncated oligopeptides corresponding to the sequence 13TPTPTPTGTQTPTT26. We found that peptides containing the 21TQTPT25 sequence were able to inhibit the 994 antibody binding and also peptides 21TQTPT25 and 17TPTGTQTPT25 were the most inhibitory compounds with the lowest IC50 value (IC50=4 and 3 microM, respectively) tested. Interestingly, 21TQTPT25 peptide adopts an unordered structure even in TFE, a solvent that promotes an ordered conformation, as detected by circular dichroism and Fourier-transform infrared spectroscopy. However, Thr at position 26 or amidation of Thr25 at the C-terminus results in a much weaker (3 orders of magnitude) MAb interaction, which can be due to the presence of a turn conformation in peptides with a T26 or an amide C-terminus. We have also observed that MAb 994 recognized two other pentapeptides with the TX1TX2T motif, like 13TPTPT17 (IC50=180 microM) and 19TGTQP23 (IC50=65 microM), whose sequences are present in the native glycoprotein. These findings might suggest that in the MUC2 tandem repeat unit there are multiple antigenic sites available for recognition in underglycosylated tumor tissue and also explain the heteroclitic nature of MAb 994.

Amino Acid Motifs↗

PubMed2003

Chemotactic activity of oligopeptides containing an EWS motif on Tetrahymena pyriformis: the effect of amidation of the C-terminal residue.

Chemotactic properties of 3-7-mer peptides containing an EWS motive and their peptide amides synthesized and characterized by us were investigated in Tetrahymena pyriformis GL model. Analysis of the peptide acids shows that SEWS possesses exceptionally strong (660%+/-21; 430%+/-18) chemoattractant ability at 10(-12) and 10(-11) m respectively. The shorter peptide (EWS) possesses chemorepellent activity, while longer peptides display neutral (WSEWS) or moderate chemoattractant (EWSEWS and GEWSEWS) chemotactic ability. Amidation of the C-terminus can significantly modify the character of peptides: it points to the conclusion that a free alpha-COOH group at this position is required for the high efficiency of SEWS, while in the shorter (EWS) and longer peptides (WSEWS and EWSEWS) amidation can result in chemoattractant ligands. Evaluation of the structure-function relationship of these compounds establishes the significance of Glu (E) with its high surface-exposed area and negatively-charged side chain. The high discriminative ability and good chemotactic responsiveness of Tetrahymena support the theory that a chemotactic signalling mechanism working in higher levels of phylogeny is a well conserved and inducible one even in protozoa.

Amides↗

PubMed2003

Monitoring folding transitions of synthetic, branched-chain polypeptides by capillary zone electrophoresis.

The coil/helix transition of a synthetic, branched-chain polymeric polypeptide (poly (Lys(Glu(1)-DL-Ala(3))EAK), 50-Lys residues long in the backbone, as a function of increasing molarities of methanol in solution, is here studied by both, circular dichroism (CD) and capillary zone electrophoresis. CD spectra showed that, at 75% v/v methanol, the transition from random coil to fully helical structure was obtained, in a pH 1.1 HCI solution in the presence of 20 mM NaCI. CZE studies, run in parallel, exhibited the classical unfolding to folding sigmoidal transition, with mid-point at 60% v/v methanol concentration, plateauing at ca. 80% v/v organic solvent. Surprisingly, though, such unfolding to folding transition was accompanied by an expansion, rather than a contraction, of the resulting ordered polypeptide. As the charge of the polypeptide (a pure polycation at a pH of 2.1 in CZE) was kept rigorously constant, a plot of the radius of the polymer along the sigmoidal transition clearly showed that the radius of gyration of the helical, structured polypeptide was in fact larger than that of the random coil. Such results were confirmed by molecular dynamics simulations, which indicated that the dimensions of such polypeptide, in alpha-helix configuration, were 8.5 nm (in length) and 3.2 nm (in diameter), whereas those of the corresponding random coil were 7.2 nm (in length) and 5.1 nm (length of shorter axis). It would thus appear that the randomized structure assumes the shape of a more compact object, roughly resembling a "rugby ball".

Buffers↗

PubMed2003

Mass spectrometric analysis of combinatorial peptide libraries derived from the tandem repeat unit of MUC2 mucin.

Four 19-member synthetic peptide libraries, based on the TX1TX2T epitope motif of the mucin-2 gastrointestinal glycoprotein (MUC2) and ranging in peptide length from dipeptides to 15-mers (XT, TXT, TQTXT and KVTPTPTPTGTQTXT), were synthesized by combinatorial solid phase peptide synthesis using the portioning-mixing combinatorial approach, and analysed by electrospray ionization mass spectrometry at different (1000-10000) resolutions. Most of the components of the individual libraries could be easily identified in a single-stage molecular mass screening experiment. The resolving power of the instrument becomes an important factor above 800-1000 Da molecular mass, when predominantly multiply charged molecular ions are formed. Approaches to the identification of isobars (glutamine/lysine), isomers leucine/isoleucine) and sequence variations by tandem mass spectrometry, and/or by high-performance liquid chromatography-mass spectrometry are outlined.

Amino Acid Sequence↗

PubMed2003

Characterization of chemotactic ability of peptides containing N-formyl-methionyl residues in Tetrahymena fMLP as a targeting ligand.

The chemotactic effects of six formylated, putatively bacterial peptides (fMLP, fMLPP, fMMM, fMP, fMV, and fMS) were studied. From the set of six peptides, only fMLP (one of the most effective chemoattractant peptides in mammals) elicited a significant positive chemotactic response in the eukaryotic ciliate Tetrahymena pyriformis, while the other formylated ligands, e.g. fMMM (which is also effective in mammals), had neutral or antagonistic effects in Tetrahymena. A study of their amino acid sequences points to an, as yet obscure, interaction between C-terminal f-Met and N-terminal aromatic Phe. Some optimal physicochemical characteristics (e.g. solvent exposed area, solubility) of the molecule may be responsible for this special feature of f-MLP at such a low level of phylogeny. This means that the unicellular Tetrahymena is able to select between related molecules, giving high priority to the molecule that is the most chemoattractive in mammals. The results call attention to the possible presence of f-Met receptors at a unicellular level and to the evolutionary conservation of chemotaxis-activating processes.

Animals↗

PubMed2003

Comparative analysis of linear antibody epitopes on human and mycobacterial 60-kDa heat shock proteins using samples of healthy blood donors.

Growing evidence suggests that anti-Hsp60 antibodies might be involved in the pathogenesis of different autoimmune diseases. Attempts were reported also on the characterization of epitope specificity of anti-Hsp60 antibodies in different infectious and autoimmune diseases. However, there is a lack of data on the occurrence and epitope specificity of anti-Hsp60 antibodies in the healthy human antibody repertoire. Therefore, the aim of our study was to demonstrate the presence of anti-Hsp60 antibodies and to investigate the epitope specificity of these antibodies using a large set of synthetic 10 mer peptides covering regions of Hsp60 with high probability of antigenicity. Here we report the identification of several linear epitopes using serum Ig (IVIG) and sera from healthy subjects by ELISA assay. We have identified two epitopes 'specific' for human Hsp60 and two different epitopes 'specific' for Hsp65. In addition, six epitopes were cross-reactive in nature, detected on both proteins. The presence of these 'specific' epitopes may explain the differences in epitope structure between Hsp60 and Hsp65 observed earlier in patients with cardiovascular disease. The binding of the IVIG preparation to Hsp60 epitopes might indicate that anti-Hsp60 autoantibodies are present in the healthy human natural autoantibody repertoire.

Amino Acid Sequence↗

PubMed2003

Binding-induced folding transitions in calpastatin subdomains A and C.

Calpastatin, the endogenous inhibitor of calpain, is an intrinsically unstructured protein proposed to undergo folding transitions upon binding to the enzyme. As this feature has never been experimentally tested, we have set out to characterize the conformation of two peptides corresponding to its conserved subdomains, A and C, known to interact with calpain in a Ca(2+)-dependent manner. The peptides are disordered in water but show a high propensity for alpha-helical conformation in the presence of trifluoroethanol. The conformational transition is sensitive to Ca(2+), and is clearly seen upon binding of the peptides to the enzyme. Secondary-structure prediction of all calpastatin sequences shows that the helix-forming potential within these regions is a conserved feature of the inhibitor. Furthermore, quantitative data on the binding strength of calpastatin fragments reveal that binding of the inhibitor is accompanied by a large decrease in its configurational entropy. Taken together, these observations point to significant binding-induced local folding transitions in calpastatin, in a way that ensures highly specific, yet reversible, action of the inhibitor.

Animals↗