Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Limited proteolysis of glutamine synthetase from Escherichia coli has been studied under nondenaturing conditions (pH 7.6, 20 degrees C). Trypsin cleaves the polypeptide chain of glutamine synthetase into two principal fragments, Mr = about 32,000 and 18,000. The covalently bound AMP group is attached to the larger fragment and its presence does not affect cleavage. Although the cleaved polypeptide chain does not dissociate under nondenaturing conditions, catalytic activity is lost. Chymotrypsin and Staphylococcus aureus protease produce similar cleavages in glutamine synthetase. The substrate L-glutamate retards tryptic as well as chymotryptic digestion. Tryptic digestion is also retarded by some of the feedback inhibitors of glutamine synthetase including CTP, L-alanine, L-serine, L-histidine, and glucosamine 6-phosphate. An implication of these findings is that there is a region of the glutamine synthetase polypeptide chain that is particularly susceptible to proteolysis. Either the glutamate and inhibitor sites are formed partly by this suceptible peptide or the binding of glutamate and some inhibitors induces conformational changes within the E. coli glutamine synthetase molecule in the region of the susceptible peptide.
 ...
PMID:Limited proteolysis of glutamine synthetase is inhibited by glutamate and by feedback inhibitors. 3 14

Analysis of platelet membrane proteins and glycoproteins by SDS polyacrylamide gel electrophoresis was carried out before and after treatment with thrombin. Extended incubation with thrombin (in the presence of EDTA or adenosine, which inhibit aggregation) produced extensive changes in the bands observed. With incubation times of a few minutes however, the changes were restricted to a glycopeptide, GP IV (approx. 90,000 Daltons) and one or two polypeptides of low molecular weight, in particular polypeptide 16 (approx. 23,000 Daltons). At 0--3 degrees C only polypeptide 16 was still hydrolyzed. Chymotrypsin, which does not activate platelets, attacked glycopeptides I, II, III but no changes were apparent in GP IV and polypeptide 16. When chymotrypsin-treated platelets were further incubated with thrombin, only GP IV and one to two low molecular weight polypeptides, especially polypeptide 16, were affected. As polypeptide 16 appears to be an integral membrane component it is possible that it, either by itself or in combination with GP IV, represents the primary thrombin substrate involved in platelet activation. Aggregated IgG, which also activates platelets, does not modify the membrane glycoproteins but does change the low molecular weight region in particular band 16.
 ...
PMID:Effects of thrombin, chymotrypsin and aggregated gamma-globulins on the proteins of the human platelet membrane. 7 80

Chymotrypsin cleaves only one of the four major polypeptides of foot-and-mouth disease virus (FMDV serotype O) in situ. This polypeptide (VP1, mol. wt. 29 X 10(3) was first cleaved into fragments of mol. wt. 20 and 9 X 10(3) and further cleavage could be prevented by the addition of a large excess of bovine serum albumin. The infectivity of the virus particles at this stage was the same as that of the intact virus although the rate of attachment to BHK 21 cells was slower and the immunogenic activity was reduced. If hydrolysis was allowed to continue, VP1 was cleaved into fragments with mol. wt. 18 and less than 9 X 10(3), similar to those obtained with trypsin and the virus particles then had a greatly reduced infectivity and a lower immunogenicity. Treatment of strains from five other serotypes of the virus with the two enzymes cleaved only VP1 in each instance and there was a corresponding loss of infectivity. The results are discussed in relation to the location and biological activity of the virus polypeptides.
 ...
PMID:Immunogenic and cell attachment sites of FMDV: further evidence for their location in a single capsid polypeptide. 19 41

1. Chymotrypsin treatment of spinach chloroplast membranes does not change the electrophoretic mobility of either chlorophyll-protein complex 1 or 2. 2. The extraction of lipids with 80% acetone after treatment of the membranes with chymotrypsin reveals that the polypeptide components of both chlorophyll-protein complexes had been extensively digested. The extraction of carotenes with petroleum ether under the same conditions does not change the electrophoretic mobility of the chlorophyll-protein complexes. 3. Fluorescence polarisation studies of chlorophyll-protein complex 2 reveal that the chymotrypsin digestion of this complex does not result in changes of mutual orientation or distance apart of chlorophyll a, chlorophyll b or carotenoid. 4. Two polypeptide components have been detected after lipid extraction of electrophoretically purified chlorophyll-protein complexes 1 and 2. The SDS molecular weights are 24 000 and 27 000 for complex 2, and 68 000 and 64 000 for complex 1. 5. We conclude that chlorophyll performs an important structural function in both chlorophyll-protein complexes.
 ...
PMID:Evidence for a structural role for chlorophyll in chlorophyll-protein complexes. 50 98

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

The AdhE protein of Escherichia coli is a homopolymer of 96-kDa subunits harboring three Fe(2+)-dependent catalytic functions: acetaldehyde-CoA dehydrogenase, alcohol dehydrogenase, and pyruvate formatelyase (PFL) deactivase. By negative staining electron microscopy, we determined a helical assembly of 20-60 subunits into rods of 45-120 nm in length. The subunit packing is widened along the helix axis when Fe2+ and NAD are present. Chymotrypsin dissects the AdhE polypeptide between Phe762 and Ser763, thereby retaining the alcohol dehydrogenase activity on the NH2-terminal core, but destroying all other activities. PFL deactivation, i.e. quenching of the glycyl radical in PFL by the AdhE protein, was examined with respect to cofactor involvements (Fe2+, NAD, and CoA). This process is coupled to NAD reduction and requires the intact CoA sulfhydryl group. Pyruvate and NADH are inhibitors that affect the steady-state level of the radical form of PFL in a reconstituted interconversion cycle. Studies of cell cultures found that PFL deactivation in situ is initiated at redox potentials of greater than or equal to +100 mV. Our results provide insights into the structure/function organization of the AdhE multienzyme and give a rationale for how its PFL radical quenching activity may be suppressed in situ to enable effective glucose fermentation.
 ...
PMID:Ultrastructure and pyruvate formate-lyase radical quenching property of the multienzymic AdhE protein of Escherichia coli. 132 57

We have previously shown that the effects of various enzyme treatments on Rh antigen-containing polypeptides in situ could be monitored by an antibody preparation which recognizes only these polypeptides following Western blotting. We now have prepared antibodies that specifically react with either the N- or C-terminal ends of Rh-related proteins. Using all three, we have established that the C-terminus of Rh(D) polypeptide is at the cell surface, whereas its N-terminal domain is situated at the cytoplasmic side of the red blood cell membrane. Chymotrypsin digestion of ghosts derived from (-D-/-D-) cells that are devoid of Rh (C/c) and (E/e) antigens produces three major Rh(D)-related fragments: the 20-Kd fragment contains the molecule's C-terminal domain, the 17-Kd fragment its N-terminus, and the 13-Kd fragment neither. However, only the 17-Kd fragment forms an immune-complex with human polyclonal anti-D, indicating that it contains the Rh(D) antigenic domain. Other findings presented here provide further evidence for a unique folding of Rh(D) polypeptide within the cell membrane and suggest that Rh(C/c) and (E/e) polypeptides, when present, may form complexes with it.
 ...
PMID:Membrane orientation of Rh(D) polypeptide and partial localization of its epitope-containing domain. 137 Jun 45

Photosystem-2 reaction centres were prepared from pea thylakoid membranes that had been photoaffinity labelled with [14C]-azidoatrazine (2-azido-4-ethylamino-6-isopropylamino-s-triazine), a derivative of the herbicide atrazine which binds to the secondary plastoquinone electron-acceptor site of photosystem 2. SDS/PAGE of the 14C-labelled reaction centres followed by fluorography revealed photoaffinity-labelled proteins of apparent molecular masses 30 kDa and 55 kDa, which corresponded to the D1 polypeptide and to an SDS-stable heterodimer of the D1 and D2 polypeptides, respectively. To obtain sequence information on the site of photoaffinity labelling, an 8-kDa photoaffinity-labelled peptide, generated by proteolysis of the reaction-centre material with trypsin, was isolated and purified to apparent homogeneity using reverse-phase and size-exclusion HPLC techniques. The amino terminus of the photoaffinity-labelled peptide was determined to be Leu-Gly-Met-Arg-Pro-Xaa-Ile-Ala-Val-Ala-Tyr by Edman sequencing. This corresponds to the amino terminus of a predicted tryptic peptide of D1 and confirms that azidoatrazine photolabels the D1 polypeptide of photosystem 2 in the region Leu137-Arg225. Chymotrypsin/trypsin digestion of photoaffinity-labelled reaction centres followed by reverse-phase HPLC was used to isolate a smaller photoaffinity-labelled peptide. On Edman sequencing, Ser-Ala were identified as the first two residues and 14C was released on the third cycle, after which further degradation was blocked. The two potential peptide fragments with Ser-Ala at the amino terminus in the region Leu137-Arg225 are Ser148-Ala-Pro and Ser212-Ala-Met. Proline is an unlikely target for reaction with the nitrene of the photoactivated azidoatrazine, and the data are thus consistent with Met214 as the site of photoaffinity labelling on D1 when thylakoid membranes are illuminated with ultraviolet irradiation in the presence of [14C]azidoatrazine.
 ...
PMID:Sequence analysis of photoaffinity-labelled peptides derived by proteolysis of photosystem-2 reaction centres from thylakoid membranes treated with [14C]azidoatrazine. 149 53

The inactivation of native glutamine synthetase (GS) from Bacillus subtilis by trypsin, chymotrypsin, or subtilisin followed pseudo-fast order kinetics. Trypsin cleaved the polypeptide chain of GS into two principal fragments, one of about 43,000 (Mr) and the other of smaller than 10,000. Chymotrypsin and subtilisin caused similar cleavage of GS. A large fragment (Mr 35,000) and one smaller than 10,000 were detected on SDS-PAGE. The nicked protein remained dodecameric, as observed on gel filtration, electrophoresis, and electron micrography. In the presence of glutamate, ATP, and Mn2+, the digestion of GS by each of the three proteases was retarded completely; however, the presence of one substrate, L-glutamate, ATP+Mn2+, or ATP+Mg2+ led to partial protection. The product, L-glutamine, did not retard but altered the susceptibility of the protease sensitive sites. Amino acid sequence analysis of the two smaller polypeptide fragments showed that the nicked region was around serine 375 and serine 311, respectively, and that both large fragments (43,000 and 35,000) were N-terminal polypeptides of GS. The serine 311 region was involved in the formation of the enzyme-substrate complex. Tyrosine 372 near serine 375 corresponded to tyrosine 397 which was adenylylated by adenyltransferase in Escherichia coli GS.
 ...
PMID:Characterization of Bacillus subtilis glutamine synthetase by limited proteolysis. 168 34

We have obtained evidence that the ligand-recognition region of the integrin beta-subunit, platelet glycoprotein IIIa (GPIIIa), is discontinuous. Receptor function can be localized to residues near the N-terminus and to the central region of the polypeptide chain. The epitope recognized by our monoclonal antibody, CS-1, which substantially inhibits fibrin(ogen) binding to ADP- and thrombin-stimulated platelets [Ramsamooj, Doellgast & Hantgan (1990) Thromb. Res. 58, 577-592], is contained within residues 349-422 of GPIIIa. This sequence is adjacent to a proteinase-resistant domain of GPIIIa which is linked by disulphide bond(s) to an N-terminal segment near to the putative Arg-Gly-Asp recognition site [D'Souza, Ginsberg, Burke, Lam & Plow (1988) Science 242, 91-93]. Limited trypsin digestion of purified platelet GPIIIa yielded a mixture of two-chain molecules comprised of an N-terminal fragment disulphide-bonded to one of four fragments, which began at residues 299, 303, 353 or 423. Tryptic cleavage of the 300-422 segment correlated with loss of immunoreactivity with anti-GPIIIa monoclonal antibody, CS-1. Chymotrypsin cleavage of GPIIIa resulted in an N-terminal 19 kDa fragment joined by at least one intrachain cystine residue to a 46 kDa polypeptide beginning at residue 349. Partial reduction with dithiothreitol released the larger chymotryptic fragment with its epitope for CS-1 intact. These results have enabled us to localize the epitope recognized by our inhibitory monoclonal antibody, CS-1, to residues 349-422 of GPIIIa. Our data are consistent with a structure in which both the N-terminal and central regions of GPIIIa, which may be in close proximity in the functional GPIIb-IIIa complex, participate in ligand binding.
 ...
PMID:Evidence that the central region of glycoprotein IIIa participates in integrin receptor function. 206 10


1 2 3 4 5 6 Next >>