Publications

2011

Felföldi G, Eleftherianos I, Ffrench-Constant RH, Venekei I.

A serine proteinase homologue, SPH-3, plays a central role in insect immunity.

J Immunol 186:4828-34

Bibó András, Kovács Mihály, Károlyi György

Internal Lever Arm Model for Myosin IIInternal Lever Arm Model for Myosin II: IUTAM Bookseries

IUTAM Bookseries

Purcell TJ, Naber N, Franks-Skiba K, Dunn AR, Eldred CC, Berger CL,Málnási-Csizmadia A, Spudich JA, Swank DM, Pate E, Cooke R.

Nucleotide pocket thermodynamics measured by EPR reveal how energy partitioning relates myosin speed to efficiency.

We have used spin-labeled ADP to investigate the dynamics of the nucleotide-binding pocket in a series of myosins, which have a range of velocities. Electron paramagnetic resonance spectroscopy reveals that the pocket is in equilibrium between open and closed conformations. In the absence of actin, the closed conformation is favored. When myosin binds actin, the open conformation becomes more favored, facilitating nucleotide release. We found that faster myosins favor a more closed pocket in the actomyosin-ADP state, with smaller values of ΔH(0) and ΔS(0), even though these myosins release ADP at a faster rate. A model involving a partitioning of free energy between work-generating steps prior to rate-limiting ADP release explains both the unexpected correlation between velocity and opening of the pocket and the observation that fast myosins are less efficient than slow myosins.

Rauscher AÁ, Simon Z, Szöllosi GJ, Gráf L, Derényi I, Malnasi-Csizmadia A.

Temperature dependence of internal friction in enzyme reactions.

FASEB J. 2011 Aug;25(8):2804-13. Epub 2011 May 9

Our aim was to elucidate the physical background of internal friction of enzyme reactions by investigating the temperature dependence of internal viscosity. By rapid transient kinetic methods, we directly measured the rate constant of trypsin 4 activation, which is an interdomain conformational rearrangement, as a function of temperature and solvent viscosity. We found that the apparent internal viscosity shows an Arrhenius-like temperature dependence, which can be characterized by the activation energy of internal friction. Glycine and alanine mutations were introduced at a single position of the hinge of the interdomain region to evaluate how the flexibility of the hinge affects internal friction. We found that the apparent activation energies of the conformational change and the internal friction are interconvertible parameters depending on the protein flexibility. The more flexible a protein was, the greater proportion of the total activation energy of the reaction was observed as the apparent activation energy of internal friction. Based on the coupling of the internal and external movements of the protein during its conformational change, we constructed a model that quantitatively relates activation energy, internal friction, and protein flexibility.

Kardos, J., Micsonai, A., Pál-Gábor, H., Petrik, E., Gráf, L., Kovács, J., Lee, Y. H., Naiki, H., Goto, Y.

Reversible heat-induced dissociation of β2-microglobulin amyloid fibrils

Biochemistry, 50, 3211-3220

Recent progress in the field of amyloid research indicates that the classical view of amyloid fibrils, being irreversibly formed highly stable structures resistant to perturbating conditions and proteolytic digestion, is getting more complex. We studied the thermal stability and heat-induced depolymerization of amyloid fibrils of β(2)-microglobulin (β2m), a protein responsible for dialysis-related amyloidosis. We found that freshly polymerized β2m fibrils at 0.1-0.3 mg/mL concentration completely dissociated to monomers upon 10 min incubation at 99 °C. Fibril depolymerization was followed by thioflavin-T fluorescence and circular dichroism spectroscopy at various temperatures. Dissociation of β2m fibrils was found to be a reversible and dynamic process reaching equilibrium between fibrils and monomers within minutes. Repolymerization experiments revealed that the number of extendable fibril ends increased significantly upon incubation at elevated temperatures suggesting that the mechanism of fibril unfolding involves two distinct processes: (1) dissociation of monomers from the fibril ends and (2) the breakage of fibrils. The breakage of fibrils may be an important in vivo factor multiplying the number of fibril nuclei and thus affecting the onset and progress of disease. We investigated the effects of some additives and different factors on the stability of amyloid fibrils. Sample aging increased the thermal stability of β2m fibril solution. 0.5 mM SDS completely prevented β2m fibrils from dissociation up to the applied highest temperature of 99 °C. The generality of our findings was proved on fibrils of K3 peptide and α-synuclein. Our simple method may also be beneficial for screening and developing amyloid-active compounds for therapeutic purposes.

Szegő, E.M., Csorba, A., Janáky, T., Kékesi, K.A., Ábrahám, I.M., Mórotz, M.G., Penke, B., Palkovits, M., Murvai, Ü., Kellermayer, M.S.Z., Kardos, J., Juhász, G.D.

Effects of Estrogen on Beta-Amyloid-Induced Cholinergic Cell Death in the Nucleus Basalis Magnocellularis

Neuroendocrinology, 93,90-105

Alzheimer disease is characterized by accumulation of β-amyloid (Aβ) and cognitive dysfunctions linked to early loss of cholinergic neurons. As estrogen-based hormone replacement therapy has beneficial effects on cognition of demented patients, and it may prevent memory impairments, we investigated the effect of estrogen-pretreatment on Aβ-induced cholinergic neurodegeneration in the nucleus basalis magnocellularis (NBM). We tested which Aβ species induces the more pronounced cholinotoxic effect in vivo. We injected different Aβ assemblies in the NBM of mice, and measured cholinergic cell and cortical fiber loss. Spherical Aβ oligomers had the most toxic effect. Pretreatment of ovariectomized mice with estrogen before Aβ injection decreased cholinergic neuron loss and partly prevented fiber degeneration. By using proteomics, we searched for proteins involved in estrogen-mediated protection and in Aβ toxicity 24 h following injection. The change in expression of, e.g., DJ-1, NADH ubiquinone oxidoreductase, ATP synthase, phosphatidylethanolamine-binding protein 1, protein phosphatase 2A and dimethylarginine dimethylaminohydrolase 1 support our hypothesis that Aβ induces mitochondrial dysfunction, decreases MAPK signaling, and increases NOS activation in NBM. On the other hand, altered expression of, e.g., MAP kinase kinase 1 and 2, protein phosphatase 1 and 2A by Aβ might increase MAPK suppression and NOS signaling in the cortical target area. Estrogen pretreatment reversed most of the changes in the proteome in both areas. Our experiments suggest that regulation of the MAPK pathway, mitochondrial pH and NO production may all contribute to Aβ toxicity, and their regulation can be prevented partly by estrogen pretreatment.

Massaoud, M. K., Marokházi, J. and Venekei, I.

Enzymatic characterization of a serralysin-like metallo-protease from the entomopathogen bacterium, Xenorhabdus.

Biochem. Biophys. Acta, 1814, 1333-1339

Abstract We investigated the enzymatic properties of a serralysin-type metalloenzyme, provisionally named as protease B, which is secreted by Xenorhabdus bacterium, and probably is the ortholog of PrA peptidase of Photorhabdus bacterium. Testing the activity on twenty-two oligopeptide substrates we found that protease B requires at least three amino acids N-terminal to the scissile bond for detectable hydrolysis. On such substrate protease B was clearly specific for positively charged residues (Arg and Lys) at the P1 substrate position and was rather permissive in the others. Interestingly however, it preferred Ser at P1 in the oligopeptide substrate which contained amino acids also C-terminal to the scissile bond, and was cleaved with the highest k(cat)/K(M) value. The pH profile of activity, similarly to other serralysins, has a wide peak with high values between pH 6.5 and 8.0. The activity was slightly increased by Cu(2+) and Co(2+) ions, it was not sensitive for serine protease inhibitors, but it was inhibited by 1,10-phenanthroline, features shared by many Zn-metalloproteases. At the same time, EDTA inhibited the activity only partially even either after long incubation or in excess amount, and Zn(2+) was inhibitory (both are unusual among serralysins). The 1,10-phenanthroline inhibited activity could be restored with the addition of Mn(2+), Cu(2+) and Co(2+) up to 90-200% of its original value, while Zn(2+) was inefficient. We propose that both the Zn inhibition of protease B activity and its resistance to EDTA inhibition might be caused by an Asp in position 191 where most of the serralysins contain Asn.

Vörös, K., Gráf, L. Jr., Prohászka, Z., Gráf, L., Szenthe, P., Kaszás, E., Böröcz, Z., Cseh, K, Kalabay, L.

Serum-fetuin-A in metabolic and inflammatory pathways in patients with myocardial infarction.

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2362.2010.02456.x/abstract

Eur. J. Clin. Invest. 41,703-709.

BACKGROUND: Although multifunctional glycoprotein α2HS-glycoprotein/human fetuin-A (AHSG) is involved in atherosclerosis, it is not clear whether high or low concentrations are more important. We studied the correlation of serum AHSG with adiponectin, leptin, resistin, C-reactive protein (CRP) and tumour necrosis factor-α (TNF-α) to see whether its metabolic effects or its involvement in subclinical inflammation are dominant in patients with established coronary disease. MATERIALS AND METHODS: In this cross-sectional study, AHSG concentration was determined in sera of 171 patients (age: 62 ± 6 years, mean ± SD) with previous myocardial STEMI infarction and normal renal function and 81 age-matched healthy controls by radial immunodiffusion. Results  Patients had increased AHSG levels (673 ± 103 vs. 619 ± 96 mg L(-1), P < 0·001) compared to controls. Obese and diabetic patients had higher AHSG concentration than those with normal BMI or without diabetes but even the latter group had elevated AHSG levels (667 ± 101 mg L(-1), n = 88) compared to controls (P = 0·002). Serum AHSG correlated negatively with adiponectin (r = -0·236, P = 0·006) even after adjusting for BMI (r = -0·177, P = 0·043). AHSG determined adiponectin levels independently from BMI, age and other adipocytokines (P = 0·014). The correlation between leptin and AHSG (r = 0·321, P = 0·021) weakened following adjustment for BMI (r = 0·209, P = 0·072). Serum AHSG did not correlate significantly with CRP, resistin and TNF-α concentrations. BMI and resistin but not AHSG determined TNF-α levels independently. CONCLUSIONS: AHSG is elevated in sera of patients with previous myocardial infarction. Association with adipokines favours the concept that AHSG is involved in atherosclerosis more likely through metabolic pathways (insulin resistance, obesity and adipocyte dysfunction) than by inflammation in patients with post-myocardial infarction.

Rapali, P., García-Mayoral, M.F., Martínez-Moreno, M., Tárnok, K., Schlett, K., Albar, J.P., a Bruix, M., Nyitray, L., Rodriguez-Crespo, I.

LC8 Dynein Light Chain (DYNLL1) Binds to the C-terminal Domain of ATM-interacting protein (ATMIN/ASCIZ) and Regulates its Subcellular Localization.

Biochem. Biophys. Res. Comm., 414(3):493-8

LC8 dynein light chain (now termed DYNLL1 and DYNLL2 in mammals), a dimeric 89 amino acid protein, is a component of the dynein multi-protein complex. However a substantial amount of DYNLL1 is not associated to microtubules and it can thus interact with dozens of cellular and viral proteins that display well-defined, short linear motifs. Using DYNLL1 as bait in a yeast two-hybrid screen of a human heart library we identified ATMIN, an ATM kinase-interacting protein, as a DYNLL1-binding partner. Interestingly, ATMIN displays at least 18 SQ/TQ motifs in its sequence and DYNLL1 is known to bind to proteins with KXTQT motifs. Using pepscan and yeast two-hybrid techniques we show that DYNLL1 binds to multiple SQ/TQ motifs present in the carboxy-terminal domain of ATMIN. Recombinant expression and purification of the DYNLL1-binding region of ATMIN allowed us to obtain a polypeptide with an apparent molecular mass in gel filtration close to 400 kDa that could bind to DYNLL1 in vitro. The NMR data-driven modelled complexes of DYNLL1 with two selected ATMIN peptides revealed a similar mode of binding to that observed between DYNLL1 and other peptide targets. Remarkably, co-expression of mCherry-DYNLL1 and GFP-ATMIN mutually affected intracellular protein localization. In GFP-ATMIN expressing-cells DNA damage induced efficiently nuclear foci formation, which was partly impeded by the presence of mCherry-DYNLL1. Thus, our results imply a potential cellular interference between DYNLL1 and ATMIN functions.

Rapali, P., Szenes, A., Radnai, L., Bakos, A., Pál, G., Nyitray, L.

DYNLL/LC8: A Light Chain Subunit of the Dynein Motor Complex and Beyond.

IF: 3,042

FEBS J, 278(17):2980-96

The LC8 family members of dynein light chains (DYNLL1 and DYNLL2 in vertebrates) are highly conserved ubiquitous eukaryotic homodimer proteins that interact, besides dynein and myosin 5a motor proteins, with a large (and still incomplete) number of proteins involved in diverse biological functions. Despite an earlier suggestion that LC8 light chains function as cargo adapters of the above molecular motors, they are now recognized as regulatory hub proteins that interact with short linear motifs located in intrinsically disordered protein segments. The most prominent LC8 function is to promote dimerization of their binding partners that are often scaffold proteins of various complexes, including the intermediate chains of the dynein motor complex. Structural and functional aspects of this intriguing hub protein will be highlighted in this minireview.

Gáspári, Z. and Nyitray, L.

Coiled coils as models of protein structure evolution

BioMol Concepts, 2:199-210

Szabó A, Héja, D., Szakács, D., Zboray K, Kékesi KA, Radisky ES, Sahin-Tóth M, Pál, G.

High-affinity small protein inhibitors of human chymotrypsin C (CTRC) selected by phage display reveal unusual preference for P4' acidic residues

J Biol Chem.

Human chymotrypsin C (CTRC) is a pancreatic protease that participates in the regulation of intestinal digestive enzyme activity. Other chymotrypsins and elastases are inactive on the regulatory sites cleaved by CTRC, suggesting that CTRC recognizes unique sequence patterns. To characterize the molecular determinants underlying CTRC specificity, we selected high-affinity substrate-like small protein inhibitors against CTRC from a phage library displaying variants of a natural chymotrypsin inhibitor from Schistocerca gregaria (SGPI-2). On the basis of the sequence pattern selected, we designed eight inhibitor variants in which amino acid residues in the reactive loop at P1 (Met or Leu), P2' (Leu or Asp) and P4' (Glu, Asp or Ala) were varied. Binding experiments with CTRC revealed that (i) inhibitors with Leu at P1 bind 10-fold stronger than those with P1 Met; (ii) Asp at P2' (versus Leu) decreases affinity but increases selectivity and (iii) Glu or Asp at P4' (versus Ala) increase affinity 10-fold. The highest affinity SGPI-2 variant (KD 20 pM) bound to CTRC 575-fold tighter than the parent molecule. The most selective inhibitor variant exhibited a KD of 110 pM and a selectivity ranging from 225-fold to 112,664-fold against other human chymotrypsins and elastases. Homology modeling and mutagenesis identified a cluster of basic amino acid residues (Lys51, Arg56 and Arg80) on the surface of human CTRC that interact with the P4' acidic residue of the inhibitor. The acidic preference of CTRC at P4' is unique among pancreatic proteases and might contribute to the high specificity of CTRC-mediated digestive enzyme regulation.

Rapali, P., Radnai, L., Süveges, D., Harmat V, Tölgyesi F, Wahlgren WY, Katona G, Nyitray, L., Pál, G.

Directed Evolution Reveals the Binding Motif Preference of the LC8/DYNLL Hub Protein and Predicts Large Numbers of Novel Binders in the Human Proteome.

PLoS ONE

LC8 dynein light chain (DYNLL) is a eukaryotic hub protein that is thought to function as a dimerization engine. Its interacting partners are involved in a wide range of cellular functions. In its dozens of hitherto identified binding partners DYNLL binds to a linear peptide segment. The known segments define a loosely characterized binding motif: [D/S]-4K-3X-2[T/V/I]-1Q0[T/V]1[D/E]2. The motifs are localized in disordered segments of the DYNLL-binding proteins and are often flanked by coiled coil or other potential dimerization domains. Based on a directed evolution approach, here we provide the first quantitative characterization of the binding preference of the DYNLL binding site. We displayed on M13 phage a naÁ¯ve peptide library with seven fully randomized positions around a fixed, naturally conserved glutamine. The peptides were presented in a bivalent manner fused to a leucine zipper mimicking the natural dimer to dimer binding stoichiometry of DYNLL-partner complexes. The phage-selected consensus sequence V-5S-4R-3G-2T-1Q0T1E2 resembles the natural one, but is extended by an additional N-terminal valine, which increases the affinity of the monomeric peptide twentyfold. Leu-zipper dimerization increases the affinity into the subnanomolar range. By comparing crystal structures of an SRGTQTE-DYNLL and a dimeric VSRGTQTE-DYNLL complex we find that the affinity enhancing valine is accommodated in a binding pocket on DYNLL. Based on the in vitro evolved sequence pattern we predict a large number of novel DYNLL binding partners in the human proteome. Among these EML3, a microtubule-binding protein involved in mitosis contains an exact match of the phage-evolved consensus and binds to DYNLL with nanomolar affinity. These results significantly widen the scope of the human interactome around DYNLL and will certainly shed more light on the biological functions and organizing role of DYNLL in the human and other eukaryotic interactomes.

Wahlgren, W.Y., Pál, G., Kardos, J., Porrogi, P., Szenthe, B., Patthy, A., Gráf, L., Katona, G.

The catalytic aspartate is protonated in the Michaelis complex formed between trypsin and an in vitro evolved substrate-like inhibitor: a refined mechanism of serine protease action

J Biol Chem. 2011 Feb 4;286(5):3587-96. Epub 2010 Nov 21.

Kocsis, A., Kékesi, KA., Szász, R., Végh, BM., Balczer, J., Dobó, J., Závodszky, P., Gál, P., Pál, G.

Selective Inhibition of the Lectin Pathway of Complement with Phage Display Selected Peptides against Mannose-Binding Lectin-Associated Serine Protease (MASP)-1 and -2: Significant Contribution of MASP-1 to Lectin Pathway Activation.

J Immunol. 2010 Oct 1;185(7):4169-78

The complement system, an essential part of the innate immune system, can be activated through three distinct routes: the classical, the alternative, and the lectin pathways. The contribution of individual activation pathways to different biological processes can be assessed by using pathway-selective inhibitors. In this paper, we report lectin pathway-specific short peptide inhibitors developed by phage display against mannose-binding lectin-associated serine proteases (MASPs), MASP-1 and MASP-2. On the basis of the selected peptide sequences, two 14-mer peptides, designated as sunflower MASP inhibitor (SFMI)-1 and SFMI-2, were produced and characterized. SFMI-1 inhibits both MASP-1 and MASP-2 with a K(I) of 65 and 1030 nM, respectively, whereas SFMI-2 inhibits only MASP-2 with a K(I) of 180 nM. Both peptides block the lectin pathway activation completely while leaving the classical and the alternative routes intact and fully functional, demonstrating that of all complement proteases only MASP-1 and/or MASP-2 are inhibited by these peptides. In a C4 deposition inhibitor assay using preactivated MASP-2, SFMI-2 is 10-fold more effective than SFMI-1 in accordance with the fact that SFMI-2 is a more potent inhibitor of MASP-2. Surprisingly, however, out of the two peptides, SFMI-1 is much more effective in preventing C3 and C4 deposition when normal human serum containing zymogen MASPs is used. This suggests that MASP-1 has a crucial role in the initiation steps of lectin pathway activation most probably by activating MASP-2. Because the lectin pathway has been implicated in several life-threatening pathological states, these inhibitors should be considered as lead compounds toward developing lectin pathway blocking therapeutics.