Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20366 (substance P)
 21,176 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The structure of rabbit procathepsin E was determined by molecular cloning of its cDNA. The proenzyme consisted of 379 amino acids and had structural features common to human and guinea-pig procathepsin E species. The highly conserved tripeptide sequence at the active site of aspartic proteinases, Asp-Thr(Ser)-Gly, is, however, replaced by Asp-Thr-Val in rabbit procathepsin E. To our knowledge, this is the first case of such a variation in aspartic proteinases. The processed form, cathepsin E, hydrolyzed various biologically active peptides maximally at around pH5. Tachykinins, such as substance P and neurokinin A, were hydrolyzed most rapidly, with specific cleavage of sequences essential for their activity. The rates of hydrolysis were several hundred-fold higher than those of cathepsin D. Furthermore, cathepsin E was able to inactivate a functional-domain peptide of fibroblast growth factor, the sequence of which resembles those of tachykinins, and it was active in the generation of functional peptides, such as endothelin and angiotensin I, from their respective precursors. Procathepsin E was detected at high levels in various fetal tissues, such as the liver, stomach and blood cells. At the adult stage, the proenzyme was detectable only in specific tissues, such as the urinary bladder, duodenum and colon. Northern-blot analysis showed similar stage-specific and tissue-specific expression of the mRNA for procathepsin E. Since tachykinins and other suited peptide substrates of cathepsin E have been shown to have mitogenic activity, (pro)cathepsin E may regulate the growth and differentiation of embryonic and fetal tissues by degrading or processing these peptides. The enzyme may also regulate the physiological activities of adult tissues which are mediated by substance P and related tachykinins.
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PMID:Rabbit procathepsin E and cathepsin E. Nucleotide sequence of cDNA, hydrolytic specificity for biologically active peptides and gene expression during development. 840 90

Of nine biological factors (ATP, bradykinin, vasopressin, substance P, angiotensin II, norepinephrine, epinephrine, 12-tetradecanoylphorbol 13-acetate (TPA), and A23187 calcium ionophore) examined, bradykinin, as well as ATP, TPA, and A23187, significantly increased the phosphorylation of epidermal growth factor (EGF) receptors and reduced the binding of EGF to their high-affinity site. The reduction in EGF binding by bradykinin, ATP, and TPA was similarly reversed by concomitant incubation with staurosporine, a protein kinase C inhibitor, implying that the phosphorylation of EGF receptors was catalyzed probably by a protein kinase C of the same or similar type in each case. This possibility was confirmed by the fact that the major phosphorylation site of EGF receptors by the stimulation with either bradykinin, ATP, or TPA was the same (Thr-654). Different from the stimulations with ATP and TPA, the effect of bradykinin of decreasing the high-affinity EGF binding was transient (a minimum binding at 2.5 min); the reduced EGF binding was, however, sustained for up to 30 min in the presence of calyculin A, a phosphoprotein phosphatase inhibitor. Moreover, the homogenate prepared from bradykinin-stimulated A-431 cells had stronger dephosphorylation activity for phosphorylated EGF receptors than that from control cells. These results suggest that bradykinin stimulates both the protein kinase C system and a phosphoprotein phosphatase(s) activity in A-431 cells. Such biphasic effects of bradykinin to phosphorylate and dephosphorylate EGF receptors via protein kinase C and a phosphoprotein phosphatase, respectively, imply a homeostatic control of receptor function in regulating phosphorylation level by the same bioactive factor.
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PMID:Bradykinin-stimulated transient modulation of epidermal growth factor receptors in A-431 human epidermoid carcinoma cells. 840 28

Substance P (SP) is a neuropeptide that mediates multiple physiological responses including transmission of painful stimuli and inflammation via an interaction with a receptor of known primary sequence. To identify the regions of the SP receptor, also termed the NK-1 receptor, involved in peptide recognition, we are using analogues of SP containing the photoreactive amino acid p-benzoyl-L-phenylalanine (Bpa). In the present study, we used radioiodinated Bpa8-SP to covalently label with high efficiency the rat SP receptor expressed in a transfected mammalian cell line. To identify the amino acid residue that serves as the site of covalent attachment, a membrane preparation of labeled receptor was subjected to partial enzymatic cleavage by trypsin. A major digestion product of 22 kDa was identified. Upon reduction with 2-mercaptoethanol the mass of this product decreased to 14 kDa. The 22-kDa tryptic fragment was purified in excellent yield by preparative SDS/PAGE under nonreducing conditions. Subcleavage with Staphylococcus aureus V8 protease and endoproteinase ArgC yielded fragments of 8.2 and 9.0 kDa, respectively. Upon reductive cleavage, the V8 protease fragment decreased to 3.0 kDa while the endoproteinase ArgC fragment decreased to 3.2 kDa. Taking into consideration enzyme specificity, molecular size, determination of the presence or absence of N-glycosylation sites, and recognition by antibodies to specific sequences of the SP receptor, the V8 protease fragment is Thr-173 to Glu-183, while the endoproteinase ArgC fragment is Val-178 to Arg-190. These two fragments share the common sequence Val-Val-Cys-Met-Ile-Glu (residues 178-183). The site of covalent attachment of radioiodinated Bpa8-SP is thus restricted to a residue within this overlap sequence. The data presented here also establish that the cysteine residue in this sequence Cys-180, which is positioned in the middle of the second extracellular loop, participates in a disulfide bond that links the first and second extracellular loops of the receptor.
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PMID:The peptide binding site of the substance P (NK-1) receptor localized by a photoreactive analogue of substance P: presence of a disulfide bond. 855 54

We report on the synthesis and the pharmacological properties of a new series of tachykinin antagonists based on the tripeptide Ac-Thr-D-Trp(CHO)-Phe-N(Me)-Bzl (1, FR113680) partly modified on the C-terminal amide part. Stereochemistry around the benzilic carbon, as well as nitrogen substitution was investigated. Selected compounds were tested on guinea pig ileum for NK-1, rat colon and rat portal vein for NK-2 and NK-3 receptors, respectively. Two of these peptides were shown to have higher tachykinin antagonist activity (pA2 > 8.8) and selectivity for NK-1 receptors compared with compound 1 taken as reference (Table 2). In addition we investigated the stability of compounds 2 and 3 on guinea pig plasma and liver homogenate.
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PMID:Synthesis and in vitro activities of highly potent and selective tripeptide antagonists of the neurokinin NK-1 receptor. 859 72

BiP is a member of the hsp70 family of proteins that is present in the endoplasmic reticulum where it functions as a molecular chaperone. Rapid quantitative assays have been used to study the effect of mutating BiP residue 229, located in the ATP binding site, from threonine to glycine. Although binding of ATP to the mutant BiP was not affected, the mutant protein possessed 10-20% of the wild-type BiP ATPase activity. Binding to a model peptide substrate, substance P (Brot et al. (1994) Proc. Natl. Acad. Sci. USA 91, 12120-12124), was twofold higher with mutant BiP at 4 degrees C than with wild-type BiP, and was ATP dependent. Under these conditions the substance P that was bound to mutant BiP, but not the wild-type, could be released by higher levels of ATP (5-10 microM), and the ratio of substance P released to ATP hydrolyzed was greater than 10. These results suggest that stoichiometric ATP hydrolysis is not required for release of a chaperone from its substrate.
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PMID:ATP hydrolysis is not required for the dissociation of a substance P.BiP complex. 866 Jun 61

Opioid agonists induced an increase in the intracellular free calcium concentration ([Ca2+]i) or an inhibition of K+ (25 mM)-stimulated increase in [Ca2+]i in different subsets of mouse dorsal root ganglion (DRG) neurons. The total neuronal population was grouped into three classes according to somatic diameter and defined as small ( < 16 microns), intermediate (16-25 microns), or large ( > 25 microns) neurons. Substance P-like immunoreactivity was detected mainly in the small and intermediate neurons. The delta, kappa, and mu opioid receptor agonists [D-Ser2,Leu5]enkephalin-Thr (DSLET), U69593, and [D-Ala2, MePhe4, Glyol5]enkephalin (DAMGO) each induced a transient increase in [Ca2+]i in a small fraction ( < 30%) of neurons. The increases in [Ca2+]i were blocked by the opioid antagonist naloxone. The dihydropyridine-sensitive calcium channel blocker nifedipine also blocked the increase in [Ca2+]i induced by 1 microM DSLET. The rank order of potency (percentage of cells responding to each opioid agonist) was DSLET > U69593 > DAMGO. The opioid-induced increase in [Ca2+]i was observed mainly in large neurons, with a low incidence in small and intermediate neurons. Opioid agonists also caused inhibition of K(+)-stimulated increases in [Ca2+]i, which were blocked by naloxone (1 microM). Inhibition of the K(+)-stimulated increase by 1 microM DSLET or U69593 was greater in small and intermediate neurons than in large neurons.
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PMID:Opioid regulation of intracellular free calcium in cultured mouse dorsal root ganglion neurons. 873 52

Total synthesis of the cyclic peptide lactone WS9326A, a potent tachykinin antagonist isolated from Streptomyces violaceoniger strain 9326, has been achieved via Cbz-Thr(Boc-allo-Thr-Asn-Ser(Bzl)-(E)delta MeTyr-Leu-D-Phe-OTce, which was cyclized (Phe and allo-Thr) using an active ester method with N-hydroxysuccinimide. Finally the unique N-acyl group, the 2-(1(Z)-pentenyl)cinnamoyl moiety, was introduced onto the amino group in the Thr unit. The key step of the synthesis involves the preparation of the E-isomer of the dehydro-N-methyltyrosine (delta MeTyr) unit. The debenzoxylation reaction of the threo- and erythro-isomer of the beta-benzoxy-N-methyltyrosine derivatives gave exclusively the Z-isomer of Cbz-Thr-delta MeTyr(MOM)-OMe, which was then converted to the desired E-isomer by photochemical isomerization of Cbz-Thr(TBDMS)-(Z)delta MeTyr(MOM)-Leu-D-Phe-OTce at a later step.
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PMID:Total synthesis of WS9326A, a potent tachykinin antagonist from Streptomyces violaceoniger. 911 39

The nicotinic acetylcholine receptor (AChR) presents two very well differentiated domains for ligand binding that account for different cholinergic properties. In the hydrophilic extracellular region of both alpha subunits there exist the binding sites for agonists such as the neurotransmitter acetylcholine (ACh) and for competitive antagonists such as d-tubocurarine. Agonists trigger the channel opening upon binding while competitive antagonists compete for the former ones and inhibit its pharmacological action. Identification of all residues involved in recognition and binding of agonist and competitive antagonists is a primary objective in order to understand which structural components are related to the physiological function of the AChR. The picture for the localisation of the agonist/competitive antagonist binding sites is now clearer in the light of newer and better experimental evidence. These sites are mainly located on both alpha subunits in a pocket approximately 30-35 A above the surface membrane. Since both alpha subunits are sequentially identical, the observed high and low affinity for agonists on the receptor is conditioned by the interaction of the alpha subunit with the delta or the gamma chain, respectively. This relationship is opposite for curare-related drugs. This molecular interaction takes place probably at the interface formed by the different subunits. The principal component for the agonist/competitive antagonist binding sites involves several aromatic residues, in addition to the cysteine pair at 192-193, in three loops-forming binding domains (loops A-C). Other residues such as the negatively changed aspartates and glutamates (loop D), Thr or Tyr (loop E), and Trp (loop F) from non-alpha subunits were also found to form the complementary component of the agonist/competitive antagonist binding sites. Neurotoxins such as alpha-, kappa-bungarotoxin and several alpha-conotoxins seem to partially overlap with the agonist/competitive antagonist binding sites at multiple point of contacts. The alpha subunits also carry the binding site for certain acetylcholinesterase inhibitors such as eserine and for the neurotransmitter 5-hydroxytryptamine which activate the receptor without interacting with the classical agonist binding sites. The link between specific subunits by means of the binding of ACh molecules might play a pivotal role in the relative shift among receptor subunits. This conformational change would allow for the opening of the intrinsic receptor cation channel transducting the external chemical signal elicited by the agonist into membrane depolarisation. The ion flux activity can be inhibited by non-competitive inhibitors (NCIs). For this kind of drugs, a population of low-affinity binding sites has been found at the lipid-protein interface of the AChR. In addition, several high-affinity binding sites have been found to be located at different rings on the M2 transmembrane domain, namely luminal binding sites. In this regard, the serine ring is the locus for exogenous NCIs such as chlorpromazine, triphenylmethylphosphonium, the local anaesthetic QX-222, phencyclidine, and trifluoromethyliodophenyldiazirine. Trifluoromethyliodophenyldiazirine also binds to the valine ring, which is the postulated site for cembranoids. Additionally, the local anaesthetic meproadifen binding site seems to be located at the outer or extracellular ring. Interestingly, the M2 domain is also the locus for endogenous NCIs such as the neuropeptide substance P and the neurotransmitter 5-hydroxytryptamine. In contrast with this fact, experimental evidence supports the hypothesis for the existence of other NCI high-affinity binding sites located not at the channel lumen but at non-luminal binding domains. (ABSTRACT TRUNCATED)
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PMID:Topology of ligand binding sites on the nicotinic acetylcholine receptor. 940 37

Peptides with substance P-like immunoreactivity, neurokinin A-like immunoreactivity and neurotensin-like immunoreactivity were isolated in pure form from an extract of the intestine of the Burmese python (Python molurus). The primary structure of python substance P (Arg-Pro-Arg-Pro-Gln-Gln-Phe-Tyr-Gly-Leu- Met-NH2) shows one amino acid substitution (Phe8-->Tyr) compared with chicken/alligator substance P and an additional substitution (Lys3-->Arg) as compared with mammalian substance P. The neurokinin A-like immunoreactivity was separated into two components. Python neuropeptide gamma (Asp-Ala-Gly-Tyr- Ser-Pro-Leu-Ser-His-Lys-Arg-His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met-NH2 shows three substitutions (Gly5-->Ser, Gln6-->Pro and Ile7-->Leu) compared with alligator neuropeptide gamma and an additional substitution (His4-->Tyr) compared with mammalian neuropeptide gamma. Python neurokinin A (His-Lys-Thr-Asp-Ser-Phe-Val-Gly- Leu-Met.NH2) is identical to human/chicken/alligator neurokinin A. Python neurotensin (pGlu-Leu-Val-His-Asn-Lys-Ala-Arg-Pro-Tyr-Ile-Leu) is identical to chicken/alligator neurotensin. The data are indicative of differential evolutionary pressure to conserve the amino acid sequences of reptilian gastrointestinal peptides.
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PMID:Tachykinins (substance P, neurokinin A and neuropeptide gamma) and neurotensin from the intestine of the Burmese python, Python molurus. 943 9

The nicotinic acetylcholine receptor (AChR) is the paradigm of the neurotransmitter-gated ion channel superfamily. The pharmacological behavior of the AChR can be described as three basic processes that progress sequentially. First, the neurotransmitter acetylcholine (ACh) binds the receptor. Next, the intrinsically coupled ion channel opens upon ACh binding with subsequent ion flux activity. Finally, the AChR becomes desensitized, a process where the ion channel becomes closed in the prolonged presence of ACh. The existing equilibrium among these physiologically relevant processes can be perturbed by the pharmacological action of different drugs. In particular, non-competitive inhibitors (NCIs) inhibit the ion flux and enhance the desensitization rate of the AChR. The action of NCIs was studied using several drugs of exogenous origin. These include compounds such as chlorpromazine (CPZ), triphenylmethylphosphonium (TPMP+), the local anesthetics QX-222 and meproadifen, trifluoromethyl-iodophenyldiazirine (TID), phencyclidine (PCP), histrionicotoxin (HTX), quinacrine, and ethidium. In order to understand the mechanism by which NCIs exert their pharmacological properties several laboratories have studied the structural characteristics of their binding sites, including their respective locations on the receptor. One of the main objectives of this review is to discuss all available experimental evidence regarding the specific localization of the binding sites for exogenous NCIs. For example, it is known that the so-called luminal NCIs bind to a series of ring-forming amino acids in the ion channel. Particularly CPZ, TPMP+, QX-222, cembranoids, and PCP bind to the serine, the threonine, and the leucine ring, whereas TID and meproadifen bind to the valine and extracellular rings, respectively. On the other hand, quinacrine and ethidium, termed non-luminal NCIs, bind to sites outside the channel lumen. Specifically, quinacrine binds to a non-annular lipid domain located approximately 7 A from the lipid-water interface and ethidium binds to the vestibule of the AChR in a site located approximately 46 A away from the membrane surface and equidistant from both ACh binding sites. The non-annular lipid domain has been suggested to be located at the intermolecular interfaces of the five AChR subunits and/or at the interstices of the four (M1-M4) transmembrane domains. One of the most important concepts in neurochemistry is that receptor proteins can be modulated by endogenous substances other than their specific agonists. Among membrane-embedded receptors, the AChR is one of the best examples of this behavior. In this regard, the AChR is non-competitively modulated by diverse molecules such as lipids (fatty acids and steroids), the neuropeptide substance P, and the neurotransmitter 5-hydroxytryptamine (5-HT). It is important to take into account that the above mentioned modulation is produced through a direct binding of these endogenous molecules to the AChR. Since this is a physiologically relevant issue, it is useful to elucidate the structural components of the binding site for each endogenous NCI. In this regard, another important aim of this work is to review all available information related to the specific localization of the binding sites for endogenous NCIs. For example, it is known that both neurotransmitters substance P and 5-HT bind to the lumen of the ion channel. Particularly, the locus for substance P is found in the deltaM2 domain, whereas the binding site for 5-HT and related compounds is putatively located on both the serine and the threonine ring. Instead, fatty acid and steroid molecules bind to non-luminal sites. More specifically, fatty acids may bind to the belt surrounding the intramembranous perimeter of the AChR, namely the annular lipid domain, and/or to the high-affinity quinacrine site which is located at a non-annular lipid domain. Additionally, steroids may bind to a site located on the extracellular hydrophi
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PMID:Binding sites for exogenous and endogenous non-competitive inhibitors of the nicotinic acetylcholine receptor. 974 59


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