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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The X-ray structure of a new crystal form of chymotrypsinogen A grown from ethanol/water has been determined at 1.8 A resolution using Patterson search techniques. The crystals are of orthorhombic space group P212121 and contain two molecules in the asymmetric unit. Both independent molecules (referred to as A and B) have been crystallographically refined to a final R value of 0.173 with reflection data to 1.8 A resolution. Owing to different crystal contacts, both independent molecules show at various sites conformational differences, especially in segments 33-38, 142-153 and 215-222. If these three loops are omitted in a comparison, the root-mean-square (r.m.s.) deviation of the main-chain atoms of molecules A and B is 0.32 A. If segments 70-79, 143-152 and 215-221 are omitted, a comparison of either molecule A or molecule B with the chymotrypsinogen model of Freer et al. (1970) reveals an r.m.s. deviation of the alpha-carbon atoms of about 0.7 A. Compared with the active enzyme, four spatially adjacent peptide segments, in particular, are differently organized in the zymogen: the amino-terminal segment 11-19 runs in a rigid but strained conformation along the molecular surface due to the covalent linkage through Cys1; also segment 184-194 is in a rigid unique conformation due to several mutually stabilizing interactions with the amino-terminal segment; segment 216-222, which also lines the specificity pocket, adapts to different crystal contacts and exists in both chymotrypsinogen molecules in different, but defined conformations; in particular, disulfide bridge 191-220, which covalently links both latter segments, has opposite handedness in molecules A and B; finally, the autolysis loop 142 to 153 is organized in a variety of ways and in its terminal part is completely disordered. Thus, the allosteric activation domain (Huber & Bode, 1978) is organized in defined although different conformations in chymotrypsinogen molecules A and B, in contrast to trypsinogen, where all four homologous segments of the activation domain are disordered. This reflects the structural variability and deformability of the activation domain in serine proteinase proenzymes. If the aforementioned peptide segments are omitted, a comparison of our chymotrypsinogen models with gamma-chymotrypsin (Cohen et al., 1981) yields an r.m.s. deviation for alpha-carbon atoms of about 0.5 A. The residues of the "active site triad" are arranged similarly, but the oxyanion hole is lacking in chymotrypsinogen.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Biol 1985 Oct 05
PMID:Bovine chymotrypsinogen A X-ray crystal structure analysis and refinement of a new crystal form at 1.8 A resolution. 405 57

The structure of the alpha 1-adrenergic receptor was investigated by comparing polypeptides identified by sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gel electrophoresis with the size of the intact receptor in cell membranes as determined by target size analysis. The alpha 1-adrenergic receptor from rat liver membranes affinity-labeled with [3H]phenoxybenzamine, a covalent affinity reagent, appeared as a single polypeptide with a molecular mass of 85,000 daltons (Da) on NaDodSO4-polyacrylamide gels. In the absence of protease inhibitors, smaller peptides of 58-62 kDa and 40-45 kDa, specifically labeled with [3H]phenoxybenzamine, were also apparent on NaDodSO4 gels. In order to determine whether the 85-kDa protein represented all or only a portion of the alpha 1-receptor, radiation inactivation (target size analysis) was undertaken. Radiation-induced receptor inactivation was measured by the loss of specific [3H]phenoxybenzamine and [3H]prazosin binding and by the loss of affinity-labeled alpha 1-adrenergic receptors on NaDodSO4 gels. Target size analysis of rat liver alpha 1-receptors indicated that the intact membrane-bound receptor has an average molecular mass of 160,000 Da. These data suggest that the intact alpha-receptor may exist in the membrane as a dimer of two 85,000-Da subunits. The structure of the alpha 1-receptor was further studied by limited proteolysis of the 85-kDa protein isolated from NaDodSO4 gels. Trypsin, chymotrypsin, and papain produce smaller peptides similar to those produced during membrane isolation in the absence of protease inhibition. Limited proteolysis of the membrane-bound receptor produces water-soluble peptides, the largest of which is 45,000 Da. This peptide contains the ligand-binding domain and protrudes from the membrane into the extracellular space.
Mol Pharmacol 1984 Sep
PMID:Alpha 1-adrenergic receptor structure. 609 Aug 81

The kinetics of glucocorticoid receptor activation and the changes in molecular properties of the receptors by the activation were studied, employing aqueous two-phase partitioning of rat thymocyte, rat liver and mouse S49.1 lymphoma cell cytosol labelled with tritiated glucocorticoid. By a mathematical analysis of the time-course of the receptor partition coefficient during activation, we demonstrate that at least two different receptor conversions take place during this process. Partitionings at conditions excluding receptor aggregation allowed an evaluation of differences in net charge between activated and non-activated forms of native and chymotrypsin-treated receptors. The net charge of the chymotrypsinized receptor changes little by the activation, being between 0 and -10 at pH 8 both in the non-activated and the activated state. In contrast, the activation changes the net charge of the native receptor from around -50 to around -10.
Mol Cell Endocrinol
PMID:Changes in net charge of glucocorticoid receptors by activation, and evidence for a biphasic activation kinetics. 618 76

The detailed immunochemistry of a limited molecular domain of carcinoembryonic antigen (CEA) was examined, by using new methods to prepare and purify immunoreactive fragments. Fragments of CEA were prepared by digestion of the reduced and alkylated glycoprotein with protease V8, chymotrypsin or trypsin, or by chemical cleavage at cysteine residues with 2-nitro-5-thiocyanobenzoic acid. The products were fractionated by high performance liquid chromatography (HPLC) on a reversed phase support, and the most immunoreactive fragment was recovered from each of the four mixtures. The Mr of these purified fragments ranged from 30,000-35,000, the amino acid compositions were similar, and all contained carbohydrate. The four independently derived fragments gave similar inhibitions of CEA binding to anti-CEA antisera; maximum values were 15-55% depending on the antiserum employed. Competitive assays with pairs of fragments in different combinations showed that the four contained essentially the same subset of antigenic determinants. The fragments were quite resistant to further enzymatic digestion, but comparison of the HPLC profiles of mild acid hydrolysates of two of the fragments showed substantial similarity. These results suggest that the CEA molecule includes a region of about 30,000 mol. wt that is contained between consecutive cysteine residues, is relatively resistant to a number of residue-specific proteases, and constitutes a significant subset of antigenic determinants. Assays to identify cleavage products with different antigenic specificities were negative, suggesting that other determinants were destroyed or that the corresponding antibody populations were too small to detect.
Mol Immunol 1983 Apr
PMID:Preparation of fragments of carcinoembryonic antigen and identification of a major subset of antigenic determinants. 619 Dec 7

Symmetry in antibody plus complement mediated killing between a T15 idiotype-bearing monoclonal antibody (HPC-M2) and an anti-T15 monoclonal antibody (B36-82) is demonstrated. The HPC-M2 antibody is also shown to be multispecific in its effector function, since it lyses both phosphorylcholine coated erythrocytes, and B36-82 Fab coated red blood cells. The symmetry and multispecificity in effector function are presented as new evidence against the concept that the paratope of antibody molecule exists as a uniquely defined site on the antibody variable region. A theoretical consequence for immune system network theory is that the anti-idiotypic set and the internal image are functionally equivalent, the results support symmetric network models of regulation, and are evidence against asymmetric models.
Mol Immunol 1983 Aug
PMID:Symmetry of effector function in the immune system network. 619 30

In attempts to produce fragments of an allergenic molecule which would retain allergenic and/or antigenic determinant(s), the cytochrome c of ryegrass (RG) pollen, which had been shown to be an allergenic constituent of this pollen, was digested with trypsin and chymotrypsin and the resulting fragments were separated by high performance liquid chromatography. Several of these fragments were shown, with the aid of the radioallergosorbent test and solid phase radioimmunoassays, to bind IgE antibodies present in a pool of six sera from grass-sensitive patients and three murine monoclonal antibodies, designated as Mab 41, Mab 42 and Mab 43, which had been originally produced against the crossreacting cytochrome c of Kentucky bluegrass (KBG). In summary, (i) fragments C-67 and C-74 reacted with all antibodies, (ii) fragments T-45, T-46 and C-69 bound to human IgE antibodies as well as to Mab 41 and Mab 42, but not to Mab 43, (iii) fragment T-44 reacted only with Mab 41 and Mab 42, and (iv) fragment C-83 bound only Mab 42 and Mab 43. On the basis of these results, it is concluded that (i) immunochemically active fragments of the RG cytochrome c can be readily produced by enzymatic degradation, (ii) there is significant crossreaction between the antigenic determinants of RG and KBG cytochromes c, (iii) whereas all fragments possessed at least two of the original antigenic determinants, fragments C-83 and T-44 were devoid of allergenic determinants, (iv) the antigenic determinants recognized by Mab 41 and Mab 42 were different from those reacting with human IgE antibodies and Mab 43, (v) each of the three monoclonal antibodies recognized a distinct antigenic determinant, (vi) fragments C-67 and C-74 possessed all determinants recognized by the human IgE and mouse antibodies used.
Mol Immunol 1984 May
PMID:Determinants of ryegrass pollen cytochrome c recognized by human IgE and murine monoclonal antibodies. 620 97

A specific antibody subpopulation(s) in antihorse cytochrome c serum was detected for peptide fragment 81-104 of cyanogen bromide (CNBr) cleaved horse cytochrome c (HCytc). This antiserum was made in the rabbit against polymeric horse cytochrome c. The presence of the peptide-specific antibody subpopulation(s) was demonstrated utilizing HCytc, CNBr-peptide 81-104 and isolated chymotrypsin-digested HCytc fragments 60-67, 83-97 and 98-104 to compete with radio-labeled peptide 81-104 and antiHCytc serum in a competitive radioimmunoassay (RIA). This antibody subpopulation(s) in antiHCytc serum was demonstrated to be specific for peptide 81-104. At the 50% inhibition level in competitive RIA, 100- and 1000-fold molar excesses of HCytc and its peptide 1-65, respectively, were required to affect an equivalent binding to that of the HCytc peptide 81-104. Competitive RIAs have been performed utilizing three different kinds of antigen to compete with HCytc peptide 81-104 and antihorse cytochrome c sera. These three kinds of antigens are: endopeptidase digests of HCytc, cytochrome c peptides 81-104 of several species and several isolated chymotryptic peptide fragments of HCytc. The results have indicated that this peptide-specific antibody subpopulations(s) in antiHCytc serum is similar to antibodies made against peptide 81-104-BSA. Regions of antigenicity have been identified at positions 92, 100, 103 and 104 with both antisera.
Mol Immunol 1984 Oct
PMID:Antibody subpopulation in antihorse cytochrome c serum. 620 69

The interaction of gonadotropin-releasing hormone (GnRH) agonists and antagonists with pituitary membranes was studied by using 125I-labeled agonist, [D-Ser(t-Bu)6, des-Gly10-ethylamide]-GnRH, and antagonist [D-pGlu1, D-Phe2, Trp3,6]-GnRH. Their binding was affected differently by cations, and by pretreatment of membranes with proteolytic enzymes and sulfhydryl-blocking reagents. Monovalent cations at millimolar concentrations (10-100 mM) and divalent cations at lower concentrations (0.5-5 mM) reduced more significantly the binding of the agonist than that of the antagonist. Pretreatment of the membranes with trypsin and chymotrypsin abolished the specific binding of both agonist and antagonist, in a dose-response manner, with the former being less affected. Pretreatment of the membranes with sulfhydryl-blocking reagents did not alter the binding of the antagonist but enhanced the binding of the agonist. This enhancement in the specific binding was found to be due to an increase in the apparent affinity of the agonist. These results may suggest that GnRH agonists and antagonists bind differently to the same receptor.
Mol Cell Endocrinol 1981 Sep
PMID:Some characteristics of GnRH receptors in rat-pituitary membranes: differences between an agonist and and antagonist. 626 24

Adenosine diphosphate (ADP) is known to induce platelet shape change, aggregation and fibrinogen binding, followed by secretion. These processes are mediated by the binding of ADP to an externally oriented protein of the platelet plasma membrane. An affinity analog of ATP, a competitive inhibitor of the action of ADP, has been utilized to probe the structure and function of this receptor. FSBA (5'-p-fluorosulfonylbenzoyl adenosine) covalently modifies a single protein in intact platelets with Mr = 100 000 and concomitantly inhibits platelet shape change, aggregation and fibrinogen binding. Studies on platelet membranes demonstrate non-covalent association of ADP-binding protein with actin which is also labeled by FSBA but only in isolated membranes. This finding suggests a structural and functional coupling of the receptor to the contractile process. The putative ADP receptor covalently modified with FSBA is cleaved by chymotrypsin, a process that reverses the inability of the platelets to bind fibrinogen. Thus, the Mr = 100 000 polypeptide may be involved in the proteolytic exposure of fibrinogen binding sites on the platelet surface. The ability of FSBA to inhibit platelet aggregation and fibrinogen binding by prostaglandin H2 derivatives and epinephrine suggest that ADP is involved in these processes. However, the interaction is not at the receptor level since shape change, stimulated by PGH2 derivatives and yohimbine (epinephrine antagonist) binding are unaffected by FSBA. Finally, the action of ADP to inhibit PGE1- or PGI2-stimulated adenylate cyclase appears to be mediated by a receptor distinct for the protein modified by FSBA.
Mol Cell Biochem 1984
PMID:Characteristics of an ADP receptor mediating platelet activation. 632 60

Bovine pituitary gonadotropin-releasing hormone (GnRH) receptors were characterized and identified utilizing a superactive GnRH analog, Buserelin [( D-Ser(t-Bu)6, des-Gly10-ethylamide]-GnRH), and a photoreactive GnRH analog, [azidobenzoyl-D- Lys6 ]-GnRH. Both analogs bind with high affinity to a single class of receptors, with apparent IC50 values of 0.5 nM and 1 nM, respectively. The binding of 125I-labeled Buserelin to pituitary membranes was inhibited, in a dose-responsive manner, by both trypsin and chymotrypsin, with the former being less effective. Neuraminidase at a concentration up to 100 micrograms/ml did not affect the binding. Lectins, such as concanavalin A and wheat-germ agglutinin, at a concentration range of 20-200 micrograms/ml had no effect on the binding, whereas soybean agglutinin at high concentrations (150 and 200 micrograms/ml) slightly inhibited the specific binding. Photoaffinity labeling of the bovine pituitary GnRH receptors resulted in the identification of two specific bands with apparent molecular weights of 60 K and 30 K daltons. The latter probably represents very low affinity binding sites. Both specific bands were sensitive to trypsin and chymotrypsin treatment but were not affected by neuraminidase treatment. These results suggest a slight difference between rat and bovine pituitary GnRH receptors.
Mol Cell Endocrinol 1984 May
PMID:Characterization of GnRH receptors in bovine pituitary membranes. 632 48


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