Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Escherichia coli GABA (gamma-aminobutyric acid) permease GabP is a prototypical APC (amine/polyamine/choline) super-family transporter that has a CAR (consensus amphipathic region) containing multiple specificity determinants, ostensibly organized on two helical surfaces, one hydrophobic [SHS (sensitive hydrophobic surface)] and the other hydrophilic [SPS (sensitive polar surface)]. To gauge the functional effects of placing alanine insertions at close intervals across the entire GabP CAR, 64 insertion variants were constructed. Insertions, particularly those in the SHS and the SPS, were highly detrimental to steady-state [(3)H]GABA accumulation. TSR (transport specificity ratio) analysis, employing [(3)H]nipecotic acid and [(14)C]GABA, showed that certain alanine insertions were associated with a specificity shift (i.e. a change in k (cat)/ K (m)). An insertion (INS Ala-269) located N-terminal to the SHS increased specificity for [(3)H]nipecotic acid relative to [(14)C]GABA, whereas an insertion (INS Ala-321) located C-terminal to the SPS had the opposite effect. Overall, the results are consistent with a working hypothesis that the GabP CAR contains extensive functional surfaces that may be manipulated by insertion mutagenesis to alter the specificity ( k (cat)/ K (m)) phenotype. The thermodynamic basis of TSR analysis provides generality, suggesting that amino acid insertions could affect specificity in many other transporters, particularly those such as the E. coli phenylalanine permease PheP [Pi, Chow and Pittard (2002) J. Bacteriol. 184, 5842-5847] that have a functionally significant CAR-like domain.
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PMID:Induction of substrate specificity shifts by placement of alanine insertions within the consensus amphipathic region of the Escherichia coli GABA (gamma-aminobutyric acid) transporter encoded by gabP. 1295 23

The Escherichia coli GABA (gamma-aminobutyric acid) permease, GabP, and other members of the APC (amine/polyamine/choline) transporter superfamily share a CAR (consensus amphipathic region) that probably contributes to solute translocation. If true, then the CAR should contain structural features that act as determinants of substrate specificity ( k (cat)/ K (m)). In order to address this question, we have developed a novel, expression-independent TSR (transport specificity ratio) analysis, and applied it to a series of 69 cysteine-scanning (single-cysteine) variants. The results indicate that GabP has multiple specificity determinants (i.e. residues at which an amino acid substitution substantially perturbs the TSR). Specificity determinants were found: (i) on a hydrophobic surface of the CAR (from Leu-267 to Ala-285), (ii) on a hydrophilic surface of the CAR (from Ser-299 to Arg-318), and (iii) in a cytoplasmic loop (His-233) between transmembrane segments 6 and 7. Overall, these observations show that (i) structural features within the CAR have a role in substrate discrimination (as might be anticipated for a transport conduit) and, interestingly, (ii) the substrate discrimination task is shared among specificity determinants that appear too widely dispersed across the GabP molecule to be in simultaneous contact with the substrates. We conclude that GabP exhibits behaviour consistent with a broadly applicable specificity delocalization principle, which is demonstrated to follow naturally from the classical notion that translocation occurs synchronously with conformational transitions that change the chemical potential of the bound ligand [Tanford (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 2882-2884].
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PMID:Use of the transport specificity ratio and cysteine-scanning mutagenesis to detect multiple substrate specificity determinants in the consensus amphipathic region of the Escherichia coli GABA (gamma-aminobutyric acid) transporter encoded by gabP. 1295 24

The pulmonary hypertensive response to pulmonary vascular obstruction caused by intravenously injected microparticles is amplified by pretreatment with N(omega)nitro-L-arginine methyl ester (L-NAME). The L-NAME prevents the synthesis of the potent vasodilator nitric oxide (NO) by inhibiting both the constitutive [endothelial NO synthase (eNOS or NOS-3)] and inducible [inducible NO synthase (iNOS or NOS-2)] forms of NO synthase. In the present study we used the selective iNOS inhibitor aminoguanidine (AG) to evaluate the role of iNOS in modulating the pulmonary hypertension (PH) triggered by microparticle injections. Experiment 1 was conducted to confirm the ability of AG to inhibit NO synthesis by iNOS in broiler peripheral blood mononuclear cells exposed to bacterial lipopolysaccharide (LPS, endotoxin). Mononuclear leukocytes treated with LPS produced 10-fold more NO than untreated (control) cells. The LPS-stimulated production of NO was partially inhibited by L-NAME and was fully inhibited by AG, thereby confirming that AG inhibits LPS-mediated iNOS activation in broilers. In Experiment 2 we evaluated the responses of male progeny from a base population (MP Base) and from a derivative line selected for one generation from the survivors of an LD50 microparticle injection (MP Select). The pulmonary arterial pressure (PAP) was lower in MP Select than in MP Base broilers. Both lines exhibited similar percentage increases in PAP after microparticles were injected, and AG modestly amplified the PH triggered by microparticles in both lines. In Experiment 3 we evaluated the responses of male progeny from a second base population (PAC Base) and from a derivative line selected for 3 generations using the unilateral pulmonary artery clamp technique (PAC Select). The PAP was lower in PAC Select than in PAC Base broilers, and both lines exhibited similar percentage increases in PAP in response to the microparticles. The PH triggered by microparticles was not amplified by AG but was doubled by L-NAME. These experiments demonstrate that during the 30 min following pulmonary vascular entrapment of microparticles, iNOS modulated the PH elicited in broilers derived from the MP pedigree line, but not in broilers from the PAC pedigree line. Different NOS-mediated responses among broiler populations may affect pulmonary hemodynamic characteristics of broiler lines selected using i.v. microparticle injections.
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PMID:Influence of aminoguanidine, an inhibitor of inducible nitric oxide synthase, on the pulmonary hypertensive response to microparticle injections in broilers. 1655 84

It has been postulated that at least part of the loss of cognitive function in aging may be the result of deficits in Ca(2+) recovery (CAR) and increased oxidative/inflammatory (OX/INF) stress signaling. However, previous research showed that aged animals supplemented with blueberry (BB) extract showed fewer deficits in CAR, as well as motor and cognitive functional deficits. A recent subsequent experiment has shown that DA- or Abeta(42)-induced deficits in CAR in primary hippocampal neuronal cells (HNC) were antagonized by BB extract, and (OX/INF) signaling was reduced. The present experiments assessed the most effective BB polyphenol fraction that could protect against OX/INF-induced deficits in CAR, ROS generation, or viability. HNCs treated with BB extract, BB fractions (e.g., proanthocyanidin, PAC), or control medium were exposed to dopamine (DA, 0.1 mM), amyloid beta (Abeta(42), 25 muM) or lipopolysaccharide (LPS, 1 microg/mL). The results indicated that the degree of protection against deficits in CAR varied as a function of the stressor and was generally greater against Abeta(42) and LPS than DA. The whole BB, anthocyanin (ANTH), and PRE-C18 fractions offered the greatest protection, whereas chlorogenic acid offered the lowest protection. Protective capabilities of the various fractions against ROS depended upon the stressor, where the BB extract and the combined PAC (high and low molecular weight) fraction offered the best protection against LPS and Abeta(42) but were less effective against DA-induced ROS. The high and low molecular weight PACs and the ANTH fractions enhanced ROS production regardless of the stressor used, and this reflected increased activation of stress signals (e.g., P38 MAPK). The viability data indicated that the whole BB and combined PAC fraction showed greater protective effects against the stressors than the more fractionated polyphenolic components. Thus, these results suggest that, except for a few instances, the lesser the polyphenolic fractionation, the greater the effects, especially with respect to prevention of ROS and stress signal generation and viability.
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PMID:Differential protection among fractionated blueberry polyphenolic families against DA-, Abeta(42)- and LPS-induced decrements in Ca(2+) buffering in primary hippocampal cells. 2059 78