Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A fragment corresponding to the intact dimeric form of the CH2 domain of rabbit IgG, including the hinge region disulfide linkage, was obtained by plasmin digestion of crystalline Fc derived from IgG by the action of papain. Identification and assessment of purity of the fragment was established by SDS-PAGE, amino acid composition analysis, N-terminus sequence and C-terminus amino acid analysis and SDS-urea-PAGE of the reduced fragment. The fragment retains serologic reactivity with anti-Fc specific antisera. Comparison of deglycosylation by endoglycosidase F indicates a more open special relationship between the two CH2 domains in the fragment than in Fc.
Mol Immunol 1986 May
PMID:Isolation and partial characterization of a fragment corresponding to the dimeric form of the CH2 domain of rabbit IgG. 309 28

Bovine IgG2a from an animal homozygous at the A-locus could be fractionated on DEAE columns into subpopulations; studies using analytical size columns showed that the number of subpopulations was dependent on the ionic strength of equilibration buffer. Subpopulations of IgG2a could be purified by this method which did not differ in their carbohydrate content but had mean Ips consistent with their elution behavior. The spectrotype of their H-chains but not their L-chains, paralleled the spectrotype of the corresponding intact IgG2a subpopulations. When papain digests of each subpopulation were fractionated by chromatofocusing, their Fc fragments eluted homogeneously with a pI ca 6.0 while their Fabs eluted heterogeneously with pIs ranging from 8 to 5. The distribution of carbohydrate among such fractions corresponded to the distribution of the Fcs. The behavior of the IgG2a Fabs on chromatofocusing paralleled the elution behavior of the parent IgG2a subpopulations from DEAE-Sephadex and the isoelectric behavior of their H-chains. The antibody activity of Fab fragments, separated by chromatofocusing, are consistent with the concept of idiotypic variation. The differential antibody activity of each intact IgG2a subpopulation for seven different antigens suggests that the ion-exchange behavior of IgG2a, in which the influence of allotypes and sub-isotypes has been excluded and for which charge-related L-chain heterogeneity is minimal, must reside in the VH-regions of the different IgG2a subpopulations. Investigators are cautioned against assigning ruminant subclass designations on the basis of subpopulations isolated by ion-exchange chromatography.
Mol Immunol 1987 Dec
PMID:The heterogeneity of bovine IgG2--III. The ion-exchange heterogeneity of IgG2a is the result of VH-region variation. 312 19

Finding novel leads from which to design drug molecules has traditionally been a matter of screening and serendipity. We present a method for finding a wide assortment of chemical structures that are complementary to the shape of a macromoleculer receptor site whose X-ray crystallographic structure is known. Each of a set of small molecules from the Cambridge Crystallographic Database (Allen; et al. J. Chem. Doc. 1973, 13, 119) is individually docked to the receptor in a number of geometrically permissible orientations with use of the docking algorithm developed by Kuntz et al. (J. Mol. Biol. 1982, 161, 269). The orientations are evaluated for goodness-of-fit, and the best are kept for further examination using the molecular mechanics program AMBER (Weiner; Kollman J. Comput. Chem. 1981, 106, 765). The shape-search algorithm finds known ligands as well as novel molecules that fit the binding site being studied. The highest scoring orientations of known ligands resemble binding modes generated by interactive modeling or determined crystallographically. We describe the application of this procedure to the binding sites of papain and carbonic anhydrase. While the compounds recovered from the Cambridge Crystallographic Database are not, themselves, likely to be inhibitors or substrates of these enzymes, we expect that the structures from such searches will be useful in the design of active compounds.
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PMID:Using shape complementarity as an initial screen in designing ligands for a receptor binding site of known three-dimensional structure. 312 88

We have analyzed the binding of IgG and fragments of IgG [Fc, F(ab')2, and Fab] to group C and G streptococci and to protein G, the IgG binding cell wall protein of these bacteria. A direct correlation (r = 0.87, P less than 0.0001) was observed when the binding of radiolabelled, polyclonal IgG F(ab')2- and Fc-fragments to 23 group C and G streptococcal strains was compared. One strain (G-148) was treated with increasing amounts of pepsin, trypsin or papain and the Fab-binding structure was found to be much more sensitive to the enzymes as compared to the Fc-binding. A 35 K fragment of protein G was coupled to Sepharose, and both radiolabelled IgG F(ab')2- and Fc-fragments bound to the Sepharose beads. Binding of IgG fragments was inhibited by intact IgG or by the homologous IgG fragment, whereas Fc-fragments did not inhibit Fab binding or vice versa. Two radiolabelled protein G-fragments (28 and 35 K) showed different binding to polyclonal IgG, IgG F(ab')2-, IgG Fab- and IgG Fc-fragments. Thus, in a dot binding assay the 35 K fragment bound all IgG fragments tested, whereas the 28 K protein G fragment bound only intact IgG and IgG Fc-fragments. These results indicate two independent and separate binding sites for Fab- and Fc-fragments on protein G. Different binding sites on protein G were also indicated by Western blot analysis of four different protein G-fragments (28, 35, 42 and 65 K). In these experiments the 28 K fragment showed affinity only for Fc-fragments, while the higher mol. wt protein G preparations bound both IgG Fab- and Fc-fragments.
Mol Immunol 1988 Feb
PMID:Streptococcal protein G has affinity for both Fab- and Fc-fragments of human IgG. 313 64

The comparison of the amino acid sequences of 5 cysteine proteinases: papain, actinidin, rat cathepsins B and H and chicken cathepsin L, demonstrates a striking homology among their sequences. The N-terminal region (residues 1-70 in papain) and C-terminal region (residues 118-212 in papain) display the highest sequence homologies, whereas the lowest sequence homologies are observed in the middle region (residues 71-117 in papain); a segment where most insertions/deletions are observed. The highest sequence homology is observed between rat cathepsin H and chicken cathepsin L. As shown by X-ray studies, papain and actinidin have a clearly defined double domain structure. Each domain contains a core of non-polar side chains, which are retained in cathepsins B, H and L, except for the non-polar residue 203 of the core which is replaced by glutamic acid in cathepsin B. The percentage and the location of alpha-helix and beta-sheets of cathepsins B, H and L, assessed using the methods of Garnier et al. (1978, J. Mol. Biol. 120, 97-120) and Chou and Fasman (1974, Biochemistry 13, 222-245), show that the main ordered structures in papain and actinidin are probably retained in cathepsins B, H and L. The differences observed occur essentially in the middle region, a place where sequences display the lowest homologies and which is far removed from the active site.
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PMID:Sequence homologies, hydrophobic profiles and secondary structures of cathepsins B, H and L: comparison with papain and actinidin. 314 20

A high affinity (Ka = 2-3 x 10(10) M-1) murine monoclonal anti-fluorescein IgM antibody (18-2-3) exhibiting low temp. insolubility in the absence of bound ligand has served as a model to study cryoprecipitation. Insolubility of 18-2-3 at low temp. (4 degrees C) had been shown to be reversible at higher temp. and in the presence of fluorescyl ligand, indicating antigen binding site involvement. The primary objectives were to isolate and identify structural component(s) responsible for insolubility at low temp. Procedures developed for production and isolation of the monomeric subunit (IgMs) involved thiol reduction and gel filtration separation in the presence of the zwitterionic detergent, CHAPS. Fab and (Fc)5 fragments generated by papain digestion were purified sequentially by gel filtration (Sephadex G-200) and affinity chromatography (fluorescein-Sepharose). A protocol for covalent labeling of Fab fragments with the fluorescent chromophore 2,5 DNS-Cl was developed in order to measure steady-state fluorescence polarization. In kinetic and equilibrium cryoprecipitation assays, nonliganded 18-2-3 IgM and IgMs demonstrated insolubility. Bound fluorescyl ligand, increased ionic strength (0.5 M NaCl) or basic pH (greater than 8.0) abrogated cryoprecipitation. Isolated Fab or (Fc)5 fragments did not exhibit low temp. insolubility. Decreased cryoprecipitation occurred when (Fc)5 fragments were added to nonliganded 18-2-3 IgM. Fluorescence polarization of 2,5 DNS Fab 18-2-3 fragments indicated lack of Fab-Fab aggregation. Results suggested that electrostatic interactions involving 18-2-3 antibody combining sites with interactive sites in the Fc region of homologous IgM were responsible for the phenomenon of cryoprecipitation.
Mol Immunol 1988 Dec
PMID:Cryoprecipitation properties of a high-affinity monoclonal IgM anti-fluorescyl antibody. 323 15

Submaxillary gland extracts have been fractionated to characterize the enzyme responsible for the T-kininogenase activity previously reported in this tissue [Damas, J. & Adam, A. (1985) Mol. Physiol 8, 307-316] and to know whether this activity could be of physiological relevance, since no enzyme reacting in catalytic amounts has been described so far to be able to release a vasoactive peptide from T-kininogen. The purified enzyme, provisionally called endopeptidase K, has an apparent Mr of 27,000 when not reduced prior to analysis but 21,000 after reduction and an acidic pI of 4.3 +/- 0.1. Antigenically, it is not related to tissue kallikrein. Upon incubation with purified T-kininogen it may induce a complete liberation of T-kinin from the precursor provided it is added in stoichiometric amounts. However, in parallel with the liberation of immunoreactive kinin, a proteolysis of T-kininogen is observed which is not restricted to the site of insertion of T-kinin as would be expected using a specific kininogenase. In agreement with these results, no change of the mean blood pressure was observed upon injection of endopeptidase K into the circulation of normal rats even if the amount of injected enzyme was up to ten times that required for tissue kallikrein to induce a significant fall in blood pressure. However, in spite of the large proteolysis induced by incubation with stoichiometric amounts of endopeptidase K, the total papain inhibiting capacity of T-kininogen as well as the value of the apparent inhibition constant, Ki, with this proteinase remained unchanged. Proteolytic fragments which retain cysteine-proteinase-inhibiting activity may therefore be released from T-kininogen by endopeptidase K more easily than immunoreactive kinin, thus emphasizing a prominent function of proteinase inhibitor or of proteinase inhibitor precursor for this molecule.
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PMID:T-kinin release from T-kininogen by rat-submaxillary-gland endopeptidase K. 327 1

Protease digestion of the ADP-ribosylated pertussis toxin substrate (PTS) protein was carried out after solubilization with SDS (Cleveland gels) and in the intact membrane. Cleveland gel analysis showed substantial similarities in the maps for the PTS component in neutrophils, platelets and erythrocytes and also in the S49 AC-lymphoma cell line. In the intact membrane ADP-ribosylation followed by digestion showed limited access of proteases to the PTS component. Of eight proteases tested, only papain and Staphylococcus aureus gave substantial digestion. This pattern was observed in the human platelet, erythrocyte and neutrophil plasma membranes. When the sequence was reversed and ADP-ribosylation was carried out after protease digestion, a very different pattern was observed with much greater susceptibility to digestion being noted with several proteases. By contrast, analysis of the murine AC-membrane showed some minor variations in the digest patterns. In addition, under all three conditions tested, maps of the cholera toxin substrate for the human platelet showed remarkable similarities to those obtained with the pertussis toxin substrate. Our results indicate that the protease sensitive sites of the alpha subunit of PTS and protection from proteolysis after ADP-ribosylation are properties which are shared by the PTS components of human platelets, erythrocytes and neutrophils.
Mol Immunol 1988 Mar
PMID:Peptide mapping studies of the pertussis toxin substrate in human neutrophils, platelets and erythrocytes. 328 41

Protein G is expressed at the cell surface of certain group C and group G streptococcal strains. The protein shows a unique and specific affinity for the Fc region of mammalian polyclonal and monoclonal immunoglobulin G (IgG). We have cloned the streptococcal gene coding for protein G into E. coli, using phage lambda as the vector. The protein G produced by E. coli infected with this phage was detected and analysed in Western blot experiments using radiolabelled IgG Fc fragments as a probe. Three major IgG Fc-binding bands were obtained corresponding to apparent mol. wts of 47,000, 57,000 and 65,000, respectively. Analysis of the expression in E. coli indicates that this heterogeneity is caused by a post-translational degradation of the molecule before lysis of the lambda infected E. coli cells occurred. The protein G produced in E. coli was purified by affinity chromatography on IgG-Sepharose followed by gel-filtration on Sephadex G-200. This highly purified E. coli-produced protein G was compared to protein G solubilized by papain from streptococci, in direct binding experiments and in a competitive binding assay. The two protein G variants were found to interact with polyclonal IgG from different species in a similar way. Streptococcal strains expressing protein G also show affinity for human albumin, and at the molecular level protein G was found to be responsible also for the binding of albumin. Thus, both E. coli-produced protein G and the proteolytic fragment of protein G obtained from streptococci, bound albumin. On the protein G molecule, two different and separate sites were found to bind IgG and albumin. Finally, when whole streptococci were incubated with human plasma, the interactions with protein G caused a coating of the bacteria with albumin and IgG, whereas other plasma proteins showed no affinity for protein G.
Mol Immunol 1987 Oct
PMID:Streptococcal protein G, expressed by streptococci or by Escherichia coli, has separate binding sites for human albumin and IgG. 331 91

The secondary structure of the recently sequenced chicken liver cathepsin L (EC 3.4.22.15) has been studied both by circular dichroism and a predictive method. The structural data provided by these approaches allow us to underline the extent of the structural similarities between cathepsin L and papain, one of the best known proteins in the cysteine proteinase family. The predictive method of Garnier et al. (J. Mol. Biol. 120 (1978) 97-120) is used to locate alpha-helix and beta-sheet segments in the cathepsin L sequence. An optimization of decision constants has been performed, using circular dichroism data, to improve good predictions. The combination of these approaches lead us to suggest that the location of ordered structures observed in papain is maintained in cathepsin L, but with an additional alpha-helix in the middle region (residues 85-108) of cathepsin L. Furthermore, we show that cathepsin L inactivation at neutral pH is correlated to the lost of alpha-helix content (40% at pH 5.8 and 17% at pH 7.0) in this protein. It appears that such an effect can be related to the change in the ionization state of histidine side-chains which are shown to be mainly located in the predicted alpha-helix regions.
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PMID:Delineation of chicken cathepsin L secondary structure; relationship between pH dependence activity and helix content. 338 72


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