| 1. |
- Eller, Marika, et al.
(författare)
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Peptide fragments of myelin basic protein as substrates of protein kinase C.
- 1992
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Ingår i: Biochemistry International. - 0158-5231. ; 27:4, s. 625-631
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Tidskriftsartikel (refereegranskat)abstract
- A set of peptides derived from myelin basic protein was synthesized and the kinetics of their phosphorylation by protein kinase C was studied. The replacement or the removal of the N-terminal Gln had no effect on the activity of the parent peptide. The removal of the following Lys or Arg led to a systematic decrease in substrate activity. The modifications in the C-terminal part of the peptide had a weaker influence on the parameters Vmax and KM than those in the N-terminal. The rather regular dependence of the activity of substrates upon their structure does not allow the strict definition of a minimum substrate for protein kinase C.
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| 2. |
- Eller, Marika, et al.
(författare)
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Studies on the substrate specificity of cAMP-dependent protein kinase using diastereomeric peptides
- 1991
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Ingår i: Biochemistry International. - 0158-5231. ; 25:3, s. 453-460
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Tidskriftsartikel (refereegranskat)abstract
- A set of six different diastereomeric hexapeptides RRASVA, each with a D-amino acid residue successively in the six positions, was synthesized and tested as substrates of protein kinase A. It was found that the peptide with D-Ser was neither a substrate, nor an inhibitor of the enzyme. The other five peptides were active as substrates with slightly lower kcat values than that of the all-L amino acid peptide. However, the apparent Km values increased by one to two orders of magnitude, especially when the second arginine or the alanine residue preceding the serine was substituted. The results are discussed.
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| 3. |
- Eller, Marika, et al.
(författare)
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Substrate specificity of protein kinase C studied with peptides containing D-amino acid residues.
- 1993
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Ingår i: Journal of Biochemistry. - 0021-924X. ; 114:2, s. 177-180
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Tidskriftsartikel (refereegranskat)abstract
- A set of stereoisomeric nonapeptides KRPSQRAKY with one, two, or all L-amino acid residues replaced by the corresponding D-amino acids, and two analogs with L- and D-threonine instead of serine, were synthesized and tested as substrates for protein kinase C. All of the peptides were phosphorylated by the enzyme. The maximal rate of the reaction with the all-D peptide was more than one order of magnitude lower than that for all-L peptide with serine. The same applied to the peptides with D-Ser or with D-Arg in position +2 with respect to Ser. The Km values for the peptides containing one D-amino acid were close to that for the prototype peptide (53 microM). On the other hand, when two or more D-amino acids were present, the Km value increased considerably. Replacement of serine by threonine also reduced the phosphorylation rate and increased the Km values. One can conclude that the stereospecificity of protein kinase C is much less pronounced than that of protein kinase A, which is in agreement with the less clearly pronounced substrate specificity of the former enzyme.
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| 4. |
- Järv, Jaak, et al.
(författare)
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Phosphorylation of Sepharose-coupled peptides by protein kinase A
- 1996
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Ingår i: Bioorganic chemistry. - : Elsevier BV. - 0045-2068. ; 24:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics of phosphorylation of the Sepharose-coupledpeptide RRASVA by catalytic subunit of proteinkinaseA, and diastereomers of this peptide, containingd-amino acids successively in each position, were studied. Coupling of these peptides with the amino and carboxyl termini to CH- and AH-Sepharoses had similar effects on the phosphorylation reaction, increasing theKmand decreasing theVvalues, respectively. The diastereomeric peptides were also phosphorylated by the enzyme and the rate of this reaction depended on the position of substitution ofl-amino acids with theird-analogs. However, this dependence was much less pronounced if compared with stereoselectivity of the enzyme in reactions with these peptides in solution: theKmvalues for the Sepharose-coupledpeptides were almost insensitive to the replacement ofl-amino acids withd-analogs and moderate stereoselectivity was revealed in the maximal velocity of the reaction. The Sepharose-coupledpeptide containingd-serine was also phosphorylated by proteinkinaseA while the same peptide in solution did not interact with the enzyme. Consequently, the polymer, enveloping the phosphorylatable peptide, may remarkably influence the recognition of the reaction site, altering both V and Km values.
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| 5. |
- Järv, Jaak, et al.
(författare)
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Quantitative structure-activity relationships in protein kinase C reaction with synthetic peptides derived from myelin basic protein
- 1996
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Ingår i: Bioorganic chemistry (Print). - : Elsevier BV. - 0045-2068. ; 24:2, s. 159-168
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Tidskriftsartikel (refereegranskat)abstract
- A set of peptides, Lys-Arg-Pro-Ser-X-Arg-Ala-Lys-Ala, where X stands for Ala, Val, Leu, Ile, Phe, Pro, Lys, Arg, Asp, Glu, Asn, Gln, and His, was synthesized and the kinetics of their phosphorylation by protein kinase C was studied. All compounds, except the peptide with Pro at the position X, were effectively phosphorylated by this enzyme, and for these substrates the kinetic constantsKm, maximal velocity constantsV, and second-order rate constantskIIwere determined. The data were analyzed by means of quantitative structure–activity relationships, taking into account hydrophobicity of the variable amino acids, bulkiness of their side groups quantified by molecular refractivity constants MR, and ionic status of these substituents by using an independent variable +1 for cationic, −1 for anionic, and 0 for nonionic substituents. These structural factors influenced theKmvalues, while the maximal velocity of phosphorylation depended mostly on the ionic status of the variable amino acid. The latter effect seems to characterize electrostatic interaction between the substrate molecule and some negative charge located in the enzyme active center.
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| 6. |
- Kuznetsov, Aleksei, et al.
(författare)
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ACE2 Peptide Fragment Interaction with Different S1 Protein Sites
- 2022
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Ingår i: International journal of peptide research and therapeutics. - : Springer Science and Business Media LLC. - 1573-3149 .- 1573-3904. ; 28:1
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Tidskriftsartikel (refereegranskat)abstract
- We study the effect of the peptide QAKTFLDKFNHEAEDLFYQ on the kinetics of the SARS-CoV-2 spike protein S1 binding to angiotensin-converting enzyme 2 (ACE2), with the aim to characterize the interaction mechanism of the SARS-CoV2 virus with its host cell. This peptide corresponds to the sequence 24-42 of the ACE2 alpha 1 domain, which marks the binding site for the S1 protein. The kinetics of S1-ACE2 complex formation was measured in the presence of various concentrations of the peptide using bio-layer interferometry. Formation of the S1-ACE2 complex was inhibited by the peptide in cases where it was preincubated with S1 protein before the binding experiment. The kinetic analysis of S1-ACE2 complex dissociation revealed that preincubation stabilized this complex, and this effect was dependent on the peptide concentration as well as the preincubation time. The results point to the formation of the ternary complex of S1 with ACE2 and the peptide. This is possible in the presence of another binding site for the S1 protein beside the receptor-binding domain for ACE2, which binds the peptide QAKTFLDKFNHEAEDLFYQ. Therefore, we conducted computational mapping of the S1 protein surface, revealing two additional binding sites located at some distance from the main receptor-binding domain on S1. We suggest the possibility to predict and test the short protein derived peptides for development of novel strategies in inhibiting virus infections.
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| 7. |
- Loog, Mart, et al.
(författare)
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Comparision of substrate specificities of protein kinases A and C based on peptide substrates
- 1994
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Ingår i: Bioorganic chemistry. - : Elsevier BV. - 0045-2068. ; 22:3, s. 328-336
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Tidskriftsartikel (refereegranskat)abstract
- Peptides, obtained by gradual removal of amino acids from both ends of pEKRPSQRSKYL, and stereoisomeric nonapeptides KRPSQRAKY with one D-amino acid residue successively in each position, were tested as substrates for protein kinase A, All these compounds were phosphorylated but at quite different rates by the enzyme. Comparison of the kinetic data with the appropriate results for protein kinase C, measured earlier, was used to analyze and compare the specificity determining factors of these enzymes. The analysis of the cross-specificity points to the possibility that only a short part, mainly the sequence of 1 to 2 amino acids around the phosphorylatable serine residue, is important for differentiation of substrates by these enzymes, while the remaining part of the peptide structure has similar influence on their reactivity in the case of these two protein kinases. Thus, the active center of these enzymes can be conventionally divided into two parts, which are responsible for selectivity and effectiveness of the phosphorylation reaction, respectively.
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