| 1. |
- Eklund, Sandra, et al.
(författare)
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Characterization of the endopeptidase activity of tripeptidyl-peptidase II
- 2012
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 424:3, s. 503-507
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Tidskriftsartikel (refereegranskat)abstract
- Tripeptidyl-peptidase II (TPP II) is a giant cytosolic peptidase with a proposed role in cellular protein degradation and protection against apoptosis. Beside its well-characterised exopeptidase activity, TPP II also has an endopeptidase activity. Little is known about this activity, and since it could be important for the physiological role of TPP II, we have investigated it in more detail. Two peptides, Nef(69-87) and LL37, were incubated with wild-type murine TPP II and variants thereof as well as TPP II from human and Drosophila melanogaster. Two intrinsically disordered proteins were also included in the study. We conclude that the endopeptidase activity is more promiscuous than previously reported. It is also clear that TPP II can attack longer disordered peptides up to 75 amino acid residues. Using a novel FRET substrate, the catalytic efficiency of the endopeptidase activity could be determined to be 5 orders of magnitude lower than for the exopeptidase activity.
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| 2. |
- Eklund, Sandra, et al.
(författare)
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Exploring the active site of tripeptidyl-peptidase II through studies of pH dependence of reaction kinetics
- 2012
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - : Elsevier BV. - 1570-9639 .- 1878-1454. ; 1824:4, s. 561-570
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Tidskriftsartikel (refereegranskat)abstract
- Tripeptidyl-peptidase II (TPP II) is a subtilisin-like serine protease which forms a large enzyme complex (> 4 MDa). It is considered a potential drug target due to its involvement in specific physiological processes. However, information is scarce concerning the kinetic characteristics of TPP II and its active site features, which are important for design of efficient inhibitors. To amend this, we probed the active site by determining the pH dependence of TPP II catalysis. Access to pure enzyme is a prerequisite for kinetic investigations and herein we introduce the first efficient purification system for heterologously expressed mammalian TPP II. The pH dependence of kinetic parameters for hydrolysis of two different chromogenic substrates, Ala-Ala-Phe-pNA and Ala-Ala-Ala-pNA, was determined for murine, human and Drosophila melanogaster TPP II as well as mutant variants thereof. The investigation demonstrated that TPP II, in contrast to subtilisin, has a bell-shaped pH dependence of kcatapp/KM probably due to deprotonation of the N-terminal amino group of the substrate at higher pH. Since both the KM and kcatapp are lower for cleavage of AAA-pNA than for AAF-pNA we propose that the former can bind non-productively to the active site of the enzyme, a phenomenon previously observed with some substrates for subtilisin. Two mutant variants, H267A and D387G, showed bell-shaped pH-dependence of kcatapp, possibly due to an impaired protonation of the leaving group. This work reveals previously unknown differences between TPP II orthologues and subtilisin as well as features that might be conserved within the entire family of subtilisin-like serine peptidases.
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| 3. |
- Eklund, Sandra, 1982-
(författare)
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Interpreting a Giant : Studies of Structure and Function of Tripeptidyl-peptidase II
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tripeptidyl-peptidase II (TPP II) is a subtilisin-like serine peptidase that forms a gigantic homooligomeric complex, and is involved in the degradation of peptides in the cytosol. In addition, TPP II has been implicated in specific cellular processes, such as apoptosis control and adipogenesis, but if this is dependent on its endo- or exopeptidase activity remains to be determined. This work is devoted to the structure and function of TPP II, and to finding connections between the two. Evolutionarily conserved regions of TPP II have been identified, and sequence signatures have been constructed as an aid in identification of TPP II homologues. The conserved regions highlight amino acid residues of potential importance to structure, function or both. In addition, the first TPP II homologue in a prokaryote has been documented, which was likely the result of a horizontal gene transfer. Substrate binding for the exopeptidase activity of TPP II has been studied through mutagenesis of Glu-331, which revealed a molecular ruler mechanism that positions substrates for cleavage at the third peptide bond from the N-terminus. Thus, the well-known tripeptidyl-releasing property of TPP II could be explained. The exopeptidase activity was also probed by pH dependence studies, which revealed that a substrate with a smaller residue in the P1 position could bind non-productively to the active site. Furthermore, a difference in the pH dependence of KM between TPP II from Drosophila and homologues from mammals indicated a difference in the configuration of the binding pockets between these species. The endopeptidase activity of TPP II has also been investigated, and was found to differ from the exopeptidase activity. The endopeptidase activity appeared to be promiscuous and the preference for basic amino acid residues in the P1 position reported earlier could not be substantiated. In conclusion, many structural and mechanistic features have been observed in this work. This might be of value to future drug discovery efforts towards TPP II, and in elucidating the physiological role of this gigantic enzyme.
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| 4. |
- Eklund, Sandra, et al.
(författare)
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Structure, Function and Evolution of a Giant Enzyme, Tripeptidyl-Peptidase II
- 2012
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Ingår i: Serine proteases. - : Nova Science Publishers, Inc.. - 9781619426696 ; , s. 55-70
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Bokkapitel (refereegranskat)abstract
- Tripeptidyl-peptidase II (TPP II) is a giant exopeptidase with an active site of the subtilisin-type. Its main function is to remove tripeptides from a free N-terminal end of longer peptides. TPP II is active at neutral pH and is dependent on the same catalytic triad as other subtilases, i.e. Asp-44, His-264 and Ser-449 (numbering for murine TPP II). Furthermore, Glu-331 has been shown to be important for binding the N-terminal amino group of the substrate. Besides its exopeptidase activity, TPP II also appears to have a low endopeptidase activity. The large subunit (138 kDa in humans) forms a >4 MDa. Oligomerisation is essential for full enzymatic activity. The recently determined hybrid structure of the TPP II spindle from Drosophila melanogaster demonstrated that the active site is localized inside the spindle and that it is a self-compartmentalizing enzyme. TPP II is present in most eukaryotes, but has not been detected in archea and the homologous genes that appear in prokaryotes are suggested to be the result of a horizontal gene transfer. A role for TPP II in degradation of the neuropeptide cholecystokinin has been suggested, and the enzyme appears to be involved in trimming of some substrates for antigen presentation. However, considering its widespread distribution, this is probably not its main physiological function. A more reasonable assumption is that the enzyme has evolved to participate in a general protein turnover in the cytosol of most cells, presumably together with the proteasome and other peptidases.
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| 5. |
- Kessler, Jan H., et al.
(författare)
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Antigen processing by nardilysin and thimet oligopeptidase generates cytotoxic T cell epitopes
- 2010
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Ingår i: Nature Immunology. - : Springer Science and Business Media LLC. - 1529-2908 .- 1529-2916. ; 12:1, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- Cytotoxic T lymphocytes (CTLs) recognize peptides presented by HLA class I molecules on the cell surface. The C terminus of these CTL epitopes is considered to be produced by the proteasome. Here we demonstrate that the cytosolic endopeptidases nardilysin and thimet oligopeptidase (TOP) complemented proteasome activity. Nardilysin and TOP were required, either together or alone, for the generation of a tumor-specific CTL epitope from PRAME, an immunodominant CTL epitope from Epstein-Barr virus protein EBNA3C, and a clinically important epitope from the melanoma protein MART-1. TOP functioned as C-terminal trimming peptidase in antigen processing, and nardilysin contributed to both the C-terminal and N-terminal generation of CTL epitopes. By broadening the antigenic peptide repertoire, nardilysin and TOP strengthen the immune defense against intracellular pathogens and cancer.
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| 6. |
- Nahálková, Jarmila, 1969-, et al.
(författare)
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TPPII, MYBBP1A and CDK2 form a protein–protein interaction network
- 2014
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier. - 0003-9861 .- 1096-0384. ; 564, s. 128-135
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Tidskriftsartikel (refereegranskat)abstract
- Tripeptidyl-peptidase II (TPPII) is an aminopeptidase with suggested regulatory effects on cell cycle, apoptosis and senescence. A protein–protein interaction study revealed that TPPII physically interacts with the tumor suppressor MYBBP1A and the cell cycle regulator protein CDK2. Mutual protein–protein interaction was detected between MYBBP1A and CDK2 as well. In situ Proximity Ligation Assay (PLA) using HEK293 cells overexpressing TPPII forming highly enzymatically active oligomeric complexes showed that the cytoplasmic interaction frequency of TPPII with MYBBP1A increased with the protein expression of TPPII and using serum-free cell growth conditions. A specific reversible inhibitor of TPPII, butabindide, suppressed the cytoplasmic interactions of TPPII and MYBBP1A both in control HEK293 and the cells overexpressing murine TPPII. The interaction of MYBBP1A with CDK2 was confirmed by in situPLA in two different mammalian cell lines. Functional link between TPPII and MYBBP1A has been verified by gene expression study during anoikis, where overexpression of TPP II decreased mRNA expression level of MYBBP1A at the cell detachment conditions. All three interacting proteins TPPII, MYBBP1A and CDK2 have been previously implicated in the research for development of tumor-suppressing agents. This is the first report presenting mutual protein–protein interaction network of these proteins.
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| 7. |
- Norrgård, Malena A, 1975-
(författare)
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Modulating Enzyme Functions by Semi-Rational Redesign and Chemical Modifications : A Study on Mu-class Glutathione Transferases
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, enzymes are extensively used for many industrial applications, this includes bulk and fine-chemical synthesis, pharmaceuticals and consumer products. Though Nature has perfected enzymes for many millions of years, they seldom reach industrial performance targets. Natural enzymes could benefit from protein redesign experiments to gain novel functions or optimize existing functions. Glutathione transferases (GSTs) are detoxification enzymes, they also display disparate functions. Two Mu-class GSTs, M1-1 and M2-2, are closely related but display dissimilar substrate selectivity profiles. Saturation mutagenesis of a previously recognized hypervariable amino acid in GST M2-2, generated twenty enzyme variants with altered substrate selectivity profiles, as well as modified thermostabilities and expressivities. This indicates an evolutionary significance; GST Mu-class enzymes could easily alter functions in a duplicate gene by a single-point mutation. To further identify residues responsible for substrate selectivity in the GST M2-2 active site, three residues were chosen for iterative saturation mutagenesis. Mutations in position10, identified as highly conserved, rendered enzyme variants with substrate selectivity profiles resembling that of specialist enzymes. Ile10 could be conserved to sustain the broad substrate acceptance displayed by GST Mu-class enzymes. Enzymes are constructed from primarily twenty amino acids, it is a reasonable assumption that expansion of the amino acid repertoire could result in functional properties that cannot be accomplished with the natural set of building blocks. A combination approach of site-directed mutagenesis and chemical modifications in GST M2-2 and GST M1-1 resulted in novel enzyme variants that displayed altered substrate selectivity patterns as well as improved enantioselectivities. The results presented in this thesis demonstrate the use of different protein redesign techniques to modulate various functions in Mu-class GSTs. These techniques could be useful in search of optimized enzyme variants for industrial targets.
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| 8. |
- Tomkinson, Birgitta, et al.
(författare)
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Tripeptidyl-peptidase II
- 2012. - 3
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Ingår i: Handbook of Proteolytic Enzymes volume 1. - : Elsevier. ; , s. 3325-3331
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Bokkapitel (refereegranskat)
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