Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The physicochemical and catalytic properties of thioredoxin-T' are described. This complemented protein structure consists of a 1:1 complex between the inactive fragments thioredoxin-T-(1--73) and thioredoxin T-(74--108). These are generated by selective trypsin cleavage at Arg-73 in lysine-modified and denatured Escherichia coli thioredoxin. Thioredoxin-T' was a slowly formed but stable complex with an apparent KD below 10(-8) M. The tryptophan fluorescence spectrum and the CD spectrum were very similar to those of native thioredoxin; some conformational differences were detected by gel chromatography and radioimmunoassay. Thioredoxin-T'-S2 was a substrate for NADPH and thioredoxin reductase and had 1--2% of the activity of native thioredoxin. This low relative activity was the result of a major increase in the Km value. Thioredoxin-(SH)2 was a hydrogen donor for E. coli ribonucleotide reductase with about 3% relative activity. These results for thioredoxin-T' are correlated with the known three-dimensional structure of thioredoxin. The microenvironment around Arg-73 that is close to the active disulfide appears to be of critical importance for the interactions of thioredoxin with thioredoxin reductase and ribonucleotide reductase.
...
PMID:Structure and enzymatic functions of thioredoxin refolded by complementation of two tryptic peptide fragments. 39 Dec 70

Using purified bacterially expressed herpes simplex virus type 1 ribonucleotide reductase large subunit (R1) and the proteolytic enzymes chymotrypsin and trypsin, we have generated stable N-terminal truncations. Chymotrypsin removes 246 amino acids from the amino terminus to produce a fragment (dN246R1) which retains full enzymic activity and affinity for the small subunit (R2). Treatment of R1 with trypsin produces a 120K protein and a cleavage at amino acid residue 305 to produce a fragment (dN305R1) which remains associated with a 33K N-terminal polypeptide. Although this 33K-dN305R1 complex retains full binding affinity for R2 its reductase activity is reduced by approximately 50%. Increasing the concentration of trypsin removes the 33K N-terminal polypeptide resulting in dN305R1 which, when bound to R2, has full ribonucleotide reductase activity. Like R1, dN246R1 and dN305R1 each exist as dimers showing that the first 305 amino acids of R1 are not necessary for dimer formation. These results indicate that, in structural studies of subunit interaction, dN246R1 or dN305R1 can be considered as suitable replacements for intact R1.
...
PMID:The unique N terminus of the herpes simplex virus type 1 large subunit is not required for ribonucleotide reductase activity. 130 56

A small redox-active protein has been purified to homogeneity from cell-free extracts of the strictly anaerobic thermophilic methanogen, Methanobacterium thermoautotrophicum (strain Marburg). The purification consisted of streptomycin sulfate and acid treatments and three chromatographic steps using Sephadex G-75, Mono Q HR 10/10, and Superose 12 HR 10/30 columns. When these procedures were carried out under strictly anaerobic conditions, approximately 3 mg of this protein could be isolated from 45 g of wet cell paste. Like the thioredoxins and glutaredoxins, it is a small acidic protein (pI = 4.2) consisting of 83 amino acids (M(r) = 9136). In the presence of dithiothreitol or dihydrolipoate, the protein serves as a hydrogen donor for the ribonucleotide reductase from Escherichia coli, and it catalyzes the reduction of insulin. However, it does not interact with the thioredoxin reductases from E. coli or Corynebacterium nephridii and does not function as a hydrogen donor for the ribonucleotide reductase of C. nephridii. The amino acid sequences determined by automated Edman degradation of the 14C-carboxymethylated protein and of peptides derived from trypsin and chymotrypsin digestions show a redox-active site -Cys-Pro-Tyr-Cys-, typical of the glutaredoxins. Its amino acid sequence shows moderate identity with the known glutaredoxins (E. coli, yeast, rabbit bone marrow, calf thymus, and pig liver) when the proteins are aligned at the active site. The secondary structure of the glutaredoxin-like protein predicted by the Chou-Fasman procedure shows that it is similar to the known glutaredoxins. However, surprisingly, the protein does not function as a glutathione-disulfide oxidoreductase in the presence of glutathione and glutathione reductase. This glutaredoxin-like protein may be a component of a ribonucleotide-reducing system distinct from the previously described systems utilizing thioredoxin or glutaredoxin.
...
PMID:The purification, characterization, and primary structure of a small redox protein from Methanobacterium thermoautotrophicum, an archaebacterium. 158 36

Ribonucleotide reductase catalyzes the rate-limiting step in the formation of 2'-deoxyribonucleoside 5'-triphosphates. It consists of two nonidentical protein subunits, the nonheme iron subunit, and the effector-binding subunit. It has previously been shown that these two components making up the active enzyme species are not coordinately synthesized or degraded. It was found that the effector-binding subunit was more sensitive to proteolysis by chymotrypsin, to heating at 55 degrees C, and to the sulfhydryl reagents, pCMB and NEM. The nonheme iron subunit was more sensitive to trypsin treatment. ATP and dATP protected the effector-binding subunit from proteolytic inactivation. Neither ATP nor CDP protected the effector-binding subunit from inactivation by the sulfhydryl reagents. These data indicate that the protein properties of the two subunits of mammalian ribonucleotide reductase are significantly different.
...
PMID:Differential sensitivities of the subunits of mammalian ribonucleotide reductase to proteases, sulfhydryl reagents, and heat. 351 48

Ribonucleotide reductase catalyzes the critical reaction in which the deoxyribonucleotides required for DNA replication are synthesized de novo. This enzyme consists of two non-identical protein subunits, both of which are required for enzymatic activity. These subunits consist of a non-heme iron and an effector-binding subunit. These subunits are not coordinately regulated as the cells pass from G1 to the S phase of the cell cycle. Studies carried out with the holoenzyme and the isolated subunits indicate that the effector-binding subunit is more susceptible to chymotrypsin and the sulfhydryl reagents, pCMB and NEM, than is the non-heme iron subunit. The non-heme iron subunit is more susceptible to trypsin than is the effector-binding subunit. The presence of ATP or dATP protects the effector-binding subunit from proteolysis by either trypsin or chymotrypsin. The loss of activity in the holoenzyme, as a result of proteolysis, parallels the loss of the particular subunit. These results demonstrate that the protein properties of the subunits are significantly different to account for the differential turnover. The binding of nucleotides to the effector-binding site(s), which in turn regulates ribonucleotide reductase activity, is very specific. Formycin 5'-triphosphate and etheno-ATP could not replace ATP in the CDP reductase reaction. 2',3'-DideoxyATP was 5-fold less active than dATP as a negative effector; etheno-dATP was not inhibitory. AraGTP and BuPdGTP could not replace dGTP as a positive effector of ADP reduction. BuPdGTP, but not araGTP, served as an inhibitor of CDP reduction. 2',3'-DideoxyTTP was much less active as either an activator of GDP reduction or an inhibitor of ADP reduction. These studies indicate that the binding to the allosteric sites is highly specific and suggest that the structural requirements for the binding of activators are different from the structural requirements for the binding of inhibitors.
...
PMID:Protein properties of the subunits of ribonucleotide reductase and the specificity of the allosteric site(s). 354 6

Thioredoxin from the cyanobacterium Anabaena 7119 serves as electron donor to ribonucleotide reductase and as a protein disulfide reductase. This small, heat-stable protein was found to have structural and functional similarities to thioredoxins from both bacterial and mammalian sources. We here report the complete primary structure of Anabaena thioredoxin. The structure was determined by analysis of peptides obtained after cleavage with cyanogen bromide, Staphylococcus aureus protease, and trypsin. The protein consists of 106 residues with the following amino acid sequence: Ser-Ala-Ala-Ala-Gln-Val-Thr-Asp- Ser-Thr-Phe-Lys-Gln-Glu-Val-Leu-Asp-Ser-Asp-Val-Pro-Val-leu-Val-Asp-Phe- Trp-Ala-Pro-Trp-Cys-Gly-Pro-Cys-Arg-Met-Val-Ala-Pro-Val-Val-Asp-Glu- Ile-Ala-Gln-Gln-Tyr-Glu-Gly-Lys-Ile-Lys-Val-Val-Lys-Val-Asn-Thr-Asp- Glu-Asn-Pro-Gln-Val-Ala-Ser-Gln-Tyr-Gly-Ile-Arg-Ser-Ile-Pro-Thr-Leu- Met-Ile-Phe-Lys-Gly-Gly-Gln-Lys-Val-Asp-Met-Val-Val-Gly-Ala-Val-Pro- Lys-Thr-Thr-Leu-Ser-Gln-Thr-Leu-Glu-Lys-His-Leu. The sequence of Anabaena thioredoxin shows a definite homology to the protein from Escherichia coli, with 49% residue identities occurring in the proteins when aligned at the active site disulfide.
...
PMID:The primary structure of thioredoxin from the filamentous cyanobacterium Anabaena sp. 7119. 392 69

The large subunit (R1) of herpes simplex virus (HSV) ribonucleotide reductase is a bifunctional protein consisting of a unique N-terminal protein kinase domain and a ribonucleotide reductase domain. Previous studies showed that the two functional domains are linked by a protease sensitive site. Here we provide evidence for two subdomains, of 30K and 53K, within the reductase domain. The two fragments, which were produced by limited proteolysis and were resistant to further degradation, remained tightly associated in a complex containing two molecules of each. They were capable of binding the R2 subunit of HSV ribonucleotide reductase with approximately the same affinity as the intact protein but the complex did not complement the small subunit (R2) to give an active enzyme. At low concentrations (0.4 micrograms/ml) of trypsin or V8 protease, cleavage between the subdomains was prevented by the presence of the N-terminal protein kinase domain. At higher protease concentrations (1 micrograms/ml) the N-terminal domain is extensively proteolysed and the 30K and 53K domains were generated. Identical results were obtained using purified R1 isolated from infected cell extracts or following expression in Escherichia coli. The origin of the two domains was investigated by N-terminal sequencing of the 53K fragment and by examining their reactivity with a panel of R1-specific monoclonal antibodies which we isolated and epitope mapped for that purpose. The trypsin cleavage site was found to lie between arginine 575 and asparagine 576, and proteolysis in this region was not prevented by the presence of R2 or the nonapeptide YAGAVVNDL. We propose that the ribonucleotide reductase region of HSV R1 exists in a two domain structure, and that the interdomain linking region is protected by the unique N terminus.
...
PMID:Identification of structural domains within the large subunit of herpes simplex virus ribonucleotide reductase. 799 27

Ribonucleotide reductase is responsible for supplying the deoxyribonucleotides required for DNA synthesis and repair. The active enzyme consists of two dissimilar protein components called R1 and R2. Immunoprecipitation of R1 and R2 proteins from [32P]orthophosphate-labeled exponentially growing mouse L cells showed that the R2 protein but not the R1 protein of ribonucleotide reductase could be phosphorylated in vivo. Two-dimensional phosphopeptide mapping experiments of trypsin-digested R2 protein showed a major spot containing more than 90% of the total radioactivity and a minor spot with the remaining radioactivity. Phosphoamino acid analysis of R2 phosphorylated protein indicated that phosphorylation occurred exclusively on serine. Protein kinase C, cAMP-dependent protein kinase, p34cdc2, and CDK2 were capable of phosphorylating the R2 protein in vitro, whereas casein kinase II was not. To determine whether any of these enzymes could phosphorylate peptides observed to be phosphorylated in actively growing cells, tryptic phosphopeptide maps of R2 that had been phosphorylated in vitro were compared with maps of R2 that had been isolated from [32P]-labeled cells. Only the phosphopeptide maps obtained with p34cdc2 and CDK2 matched the pattern found in [32P]-labeled cells. Experiments in which tryptic digests from different samples were mixed prior to two-dimensional separation demonstrated comigration of phosphopeptides obtained by in vivo phosphorylation with phosphopeptides derived from p34cdc2 or CDK2 obtained by in vitro phosphorylations. These studies indicate that protein R2 phosphorylation may play an important role in the regulation of ribonucleotide reduction, DNA synthesis, and cell cycle progression, and suggest a potentially important p34cdc2 and/or CDK2 regulation point in DNA replication.
...
PMID:Phosphorylation of ribonucleotide reductase R2 protein: in vivo and in vitro evidence of a role for p34cdc2 and CDK2 protein kinases. 825 5

Incubation of the C225S mutant of the R1 subunit of ribonucleotide reductase from Escherichia coli with the R2 subunit and nucleoside diphosphates leads to fragmentation of the polypeptide backbone of R1 [Mao, S. S., Holler, T. P., Bollinger, J.M., Jr., Yu, G. X., Johnston, M.I., & Stubbe, J. (1992) Biochemistry 31, 9744--9751]. The 26 and 60 kDa cleavage fragments were purified to homogeneity. The 26 kDa polypeptide was digested with Lys-C, and the peptides were partially purified by RP-HPLC. Mass spectrometric analysis (MALDI-TOF) of the HPLC fractions allowed the identification of the C-terminal peptide. The molecular mass of this peptide (2176) revealed that serine-224 constitutes its C-terminus, and further analysis of the distribution of its monoisotopic masses by FAB-MS indicated that Ser224 possesses a carboxamide rather than a carboxylate group. Treatment of the 60 kDa cleavage fragment with cyanogen bromide and subsequent MALDI-TOF analysis of the partially RP-HPLC purified peptides yielded a fraction containing its N-terminal peptide. This peptide was digested with trypsin, and the digestion mixture was purified by HPLC. Analysis of the fractions by MALDI-TOF identified the N-terminal peptide and determined a mass of 2222. This mass suggested valine 226 was the N-terminal residue (modified by an adduct of 28 mass units). Larger amounts of the C-terminal tetrapeptide of the 60 kDa fragment (V226LIE229) were obtained by complete digestion of the crude reaction mixture with endoproteinase Glu-C. The peptide mixture was then purified on an immunoadsorbent column containing immobilized antibodies raised against a synthetic peptide with the sequence KVLIE. After elution of the affinity-bound peptide, it was analyzed by CID-MS verifying that an adduct of 28 mass units was attached to valine 226. These results indicated that the amino group of Val226 is formylated. The localization of the residues at the cleavage site of C225SR1 provides a biochemical identification of the active site region of the R1 subunit of RDPR from E.coli. The details of the mechanism of cleavage remain to be elucidated.
...
PMID:Identification of an active site residue of the R1 subunit of ribonucleotide reductase from Escherichia coli: characterization of substrate-induced polypeptide cleavage by C225SR1. 875 68

The large subunit of herpes simplex virus type 2 (HSV-2) ribonucleotide reductase (ICP10) was identified in sucrose gradient-purified HSV-2 virions by immunoprecipitation/immunoblotting with antibody specific for the protein kinase (PK) domain. Immunoblotting of individual gradient fractions indicated that ICP10 cosediments with the major capsid protein and the highest virus titers. ICP10 was not labeled by iodination of purified virions, indicating that it is not located on the virion surface. After envelope glycoproteins were removed by detergent treatment, ICP10 was associated with capsid-tegument particles and became sensitive to trypsin digestion. The capsid-tegument-associated ICP10 was phosphorylated and had PK activity in vitro and on Immobilon membranes. A mutant ICP10 protein deleted in the PK domain (p95) was also associated with purified virions (ICP10deltaPK virus) but it lacked PK activity. The data indicate that ICP10 is contained within the tegument component where it retains intrinsic PK activity.
...
PMID:The large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10) is associated with the virion tegument and has PK activity. 926 54


1 2 Next >>

---