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At least 199 records · Page 11Linked to original sources
PubMed1985

A highly active chemotactic peptide analog incorporating the unusual residue 1-aminocyclohexanecarboxylic acid at position 2.

Analogs of chemotactic peptides (Formyl-Met-X-Phe-OMe) containing the stereochemically constrained residues alpha-aminoisobutyric acid (Aib), 1-aminocyclopentanecarboxylic acid (Acc5) and 1-aminocyclohexanecarboxylic acid (Acc6) at position 2 are compared with the parent sequence (X = Leu) for their ability to induce lysozyme release in rabbit neutrophils. The Acc6 analog is about 78 times more active than the parent peptide, For-Met-Leu-Phe-OH, whereas Aib and Acc5 analogs are approximately 3 and 2 times, respectively, less active than the parent peptide. NMR and model building studies clearly favour a Met-Acc6 beta-turn solution conformation in the Acc6 analog, suggesting that the neutrophil receptor is capable of recognizing a folded peptide structure. The significant differences in the activities of the Acc5 and Acc6 analogs suggest an important role for the residue 2 sidechain in receptor interactions.

Amino Acids↗
PubMed1984

Inhibitory action of aurintricarboxylic acid and rifamycin AF/013 at the polynucleotide domain of 1,25-dihydroxyvitamin D3-receptor complexes.

The binding of 1,25-dihydroxyvitamin D3-receptor complexes from chicken intestine to DNA-cellulose and isolated intestinal nuclei is inhibited in a dose-dependent manner by aurintricarboxylic acid and rifamycin AF/013. Since both nuclear- and cytoplasmic-associated receptors have been identified, some experiments were carried out on both populations of receptors. Concentrations resulting in 50% displacement of cytoplasmic receptor complexes were 3.2 X 10(-6) M and 1.2 X 10(-4) M for aurintricarboxylic acid and rifamycin AF/013 respectively. Moreover, rifamycin AF/013 was approximately nine times more potent at inhibiting nuclear receptor binding to DNA-cellulose compared to cytoplasmic receptors. Contrary to these findings, rifampicin, which does not inhibit eukaryotic RNA or DNA polymerases, did not cause a loss of receptor complex binding to DNA-cellulose at the doses tested. Neither aurintricarboxylic acid, rifampicin, nor rifamycin AF/013 resulted in any significant loss of sterol binding. Inhibition of receptor binding to DNA-cellulose by these polymerase inhibitors was not due to alteration of the DNA and was reversed by dialysis. Incubation of receptor complexes with aurintricarboxylic acid or rifamycin AF/013 inhibited binding to Cibacron blue-agarose and phosphocellulose. Furthermore, these polymerase inhibitors were utilized specifically to desorb receptor complexes from Cibacron blue-agarose columns. Sucrose density gradient analysis of inhibitor treated and untreated receptor revealed that rifamycin AF/013 treatment resulted in the appearance of a broadened 3.7 S sedimenting receptor in addition to specific bound 1,25-dihydroxyvitamin D3 in the 6.0 S region and in the pellet of the gradient.

Animals↗
PubMed1994

GABA in the inferior colliculus plays a critical role in control of audiogenic seizures.

Previous studies have implicated a decreased efficacy of GABA as an important defect subserving the audiogenic seizures of the genetically epilepsy-prone rat (GEPR-9). The inferior colliculus (IC) is a critical site for audiogenic seizure (AGS) initiation, and the pontine reticular formation (PRF) is implicated in the propagation of AGS and in other generalized seizure models. The present study observed that microinjection of baclofen, a GABA-B receptor agonist, into IC protects against AGS, and blockade of the breakdown of endogenous GABA by gabaculine, a GABA transaminase inhibitor, increased GABA levels and blocked AGS susceptibility in the GEPR-9. Microinjection of baclofen or gabaculine into the PRF reduced AGS severity, but the doses required were considerably greater and the degree of anticonvulsant effect was less. Uptake of [3H]GABA into GEPR-9 synaptosomes from the IC is significantly increased as compared to normal, which could contribute to the diminished effectiveness of GABA in the GEPR-9. Previous studies indicate that GABA-A receptor agonists block AGS with IC microinjection, and recent data indicate that blockade of GABA uptake in this nucleus significantly reduced AGS severity. These data taken together strongly support the critical importance of the defect in GABA function in the IC in modulating susceptibility to audiogenic seizure initiation in the GEPR-9.

Acoustic Stimulation↗
PubMed1987

Accumulation kinetics of cotton late embryogenesis-abundant mRNAs and storage protein mRNAs: coordinate regulation during embryogenesis and the role of abscisic acid.

The accumulation of total RNA transcripts of 18 late embryo-abundant (Lea) gene families, each encoding two closely related Lea mRNAs, was measured in cotyledon total RNA during embryogenesis and germination of Gossypium hirsutum L. by RNA dot hybridization. Transcript abundance of the three storage protein families was also followed. The Lea mRNAs belong to only two related groups of commonly regulated mRNAs. The transcript level of each of the 6 members of Class I has two transient maxima during early maturation and a maximum level at 3 days prior to desiccation. The transcript level of each of the 12 members of Class II increases abruptly in late maturation with a maximum concentration at 3 days before desiccation (Class IIA) or at desiccation (Class IIB). Several patterns of early accumulation also exist within Class II, some overlapping with those of storage protein or Lea Class I mRNAs. The concentrations of Lea mRNAs increase at least 10- to 1700-fold during embryogenesis and decline 15- to 220-fold during the first day of germination. Earlier studies indicated that most Lea mRNAs, but no storage protein mRNAs, are induced in excised embryos exposed to abscisic acid (ABA). Free (+)ABA was measured during embryogenesis using a monoclonal antibody-based ELISA. The ABA concentration shows maxima correlating with the maxima in early Class I Lea mRNA abundance. However, ABA declines during the accumulation of Class I and Class II Lea mRNAs in late embryogenesis. Consequently, ABA could be an endogenous regulator of Class I Lea mRNAs during early maturation but is not the primary regulator of Lea mRNAs during late maturation. In contrast, cotyledon water potential exhibits a decrease that correlates with the late induction of Lea mRNAs. These findings are consistent with the hypothesis that low water potential is the endogenous regulator of some ABA-inducible mRNAs. The cessation of vascular flow to the embryo may also be involved in the disappearance of storage protein mRNAs and the late induction of Lea mRNAs.

Abscisic Acid↗
PubMed1990

The role of bicuculline, aminooxyacetic acid and gabaculine in the modulation of ethanol-induced motor impairment.

Ethanol's intoxicating effects may result from ethanol-induced changes in central gamma-aminobutyric acid (GABA) mechanisms. To further test this hypothesis, mice were pretreated with bicuculline (1 mg/kg s.c.), aminooxyacetic acid (15, 20, 25 or 30 mg/kg i.p.) or gabaculine (20 or 40 mg/kg i.p.). Following pretreatment, 20% ethanol (2.25 g/kg i.p.) was administered and rolling roller performance evaluated. All ethanol-treated control animals showed lack of rolling roller performance at 5 min post ethanol but regained rolling roller performance by 35 min. Only 42% of the bicuculline pretreated mice demonstrated lack of rolling roller performance at 5 min post ethanol and all regained rolling roller performance by 15 min. Impairment of rolling roller performance by ethanol was potentiated by aminooxyacetic acid in a dose-dependent manner. Aminooxyacetic acid (25 and 30 mg/kg doses) slowed blood ethanol disappearance although analysis of blood ethanol disappearance and motor impairment curves indicated that aminooxyacetic acid potentiation of ethanol-induced rolling roller performance impairment cannot be attributed solely to aminooxyacetic acid's effect on blood ethanol levels. Gabaculine also potentiated ethanol's impairment of rolling roller performance but was more effective than aminooxyacetic acid in slowing ethanol disappearance, suggesting that in comparison to aminooxyacetic acid, alteration of ethanol metabolism plays a greater role in gabaculine's potentiation of ethanol-induced motor impairment.

Acetates↗
PubMed1982

Inhibition of nuclear uptake of glucocorticoid-receptor complex by aurintricarboxylic acid.

The presence of 50-200 microM aurintricarboxylic acid (ATA) blocked the uptake of [3H]-triamcinolone acetonide (3H-TA)-receptor complex from rat liver cytosol by isolated nuclei. The half-maximal inhibition (I.D.50) in the nuclear uptake of [3H]-TA-receptor complex was observed at 70- and 80 microM ATA depending upon whether the inhibitor was added prior to or following receptor activation. In addition, the nuclear-bound [3H]-TA-receptor complex from control samples could be completely extracted by an incubation with 20-100 microM ATA. The amount of [3H]-TA-receptor complex remained unchanged under these conditions. The effects of ATA may result due to its interaction with the glucocorticoid receptor at/near the sites that are involved in its nuclear uptake. ATA, therefore is a potentially useful chemical probe for analysis of glucocorticoid receptor.

Adrenalectomy↗
PubMed1985

Interaction of chick oviduct progesterone receptor with immobilized aurintricarboxylic acid.

Aurintricarboxylic acid (ATA) was immobilized on Sepharose 4B via a carbodiimide coupling mechanism. A majority of the chick oviduct progesterone receptor was retained on the affinity resin and could be recovered upon washing the column with buffer containing free ligand or 3 M guanidine-HCl. The [3H]progesterone-receptor complex retained its integrity following the chromatography on ATA-Sepharose as judged by sedimentation analysis. The procedure allowed significant purification of progesterone receptor: SDS-polyacrylamide gel electrophoresis of the purified preparation revealed elimination of many peptide bands present in the cytosol prior to ATA-Sepharose chromatography. The technique thus has a clear potential in characterization and purification of progesterone receptor.

Animals↗
PubMed1985

Incorporation of chorismic acid and 4-aminobenzoic acid into the 4-hydroxyaniline moiety of N-(gamma-L-glutamyl)-4-hydroxyaniline in Agaricus bisporus.

Agaricus bisporus contains the unique aniline derivative, N-(gamma-L-glutamyl)-4-hydroxyaniline. 14C-labelled chorismic acid was quantitatively incorporated into the 4-hydroxyaniline moiety of this aniline derivative, whereas 14C-labelled prephenic acid and anthranilic acid were not incorporated into 4-hydroxyaniline. These observations indicate the branch point of the biosynthetic route of 4-hydroxyaniline in the shikimic acid pathway to be chorismic acid. Moreover, 4-aminobenzoic acid proved to be an effective precursor of 4-hydroxyaniline.

4-Aminobenzoic Acid↗
PubMed1990

Overexpression, purification, and characterization of isochorismate synthase (EntC), the first enzyme involved in the biosynthesis of enterobactin from chorismate.

Isochorismate synthase (EC 5.4.99.6), the entC gene product of Escherichia coli, catalyzes the conversion of chorismate to isochorismate, the first step in the biosynthesis of the powerful iron-chelating agent enterobactin. A sequence-specific deletion method has been used to construct an EntC overproducer, which allows for the purification and characterization of the E. coli isochorismate synthase for the first time. The N-terminal sequence and the subunit molecular weight (43,000) of the polypeptide derived from SDS-polyacrylamide gel electrophoresis agree with those deduced from DNA sequence data. The enzyme is an active monomer with a native molecular weight of 42,000. It was shown that EntC alone is fully capable of catalyzing the interconversion of chorismate and isochorismate in both directions and the associated activity is not affected by EntA of the same biosynthetic pathway as has recently been speculated [Elkins, M. F., & Earhart, C. F. (1988) FEMS Microbiol. Lett. 56, 35; Liu, J., Duncan, K., & Walsh, C.T. (1989) J. Bacteriol. 171, 791; Ozenberger, B. A., Brickman, T.J., & McIntosh, M. A. (1989) J. Bacteriol. 171, 775]. The kinetic constants were determined with Km = 14 microM and kcat = 173 min-1 for chorismate in the forward direction and Km = 5 microM and kcat = 108 min-1 for isochorismate in the backward direction. The equilibrium constant for the reaction derived from the kinetic data is 0.56 with the equilibrium lying toward the side of chorismate, corresponding to a free energy difference of 0.36 kcal/mol between chorismate and isochorismate.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1997

Residue-based control of helix shape in beta-peptide oligomers.

Proteins and RNA are unique among known polymers in their ability to adopt compact and well-defined folding patterns. These two biopolymers can perform complex chemical operations such as catalysis and highly selective recognition, and these functions are linked to folding in that the creation of an active site requires proper juxtaposition of reactive groups. So the development of new types of polymeric backbones with well-defined and predictable folding propensities ('foldamers') might lead to molecules with useful functions. The first step in foldamer development is to identify synthetic oligomers with specific secondary structural preferences. Whereas alpha-amino acids can adopt the well-known alpha-helical motif of proteins, it was shown recently that beta-peptides constructed from carefully chosen beta-amino acids can adopt a different, stable helical conformation defined by interwoven 14-membered-ring hydrogen bonds (a 14-helix; Fig. 1a). Here we report that beta-amino acids can also be used to design beta-peptides with a very different secondary structure, a 12-helix (Fig. 1a). This demonstrates that by altering the nature of beta-peptide residues, one can exert rational control over the secondary structure.

Amino Acids↗
PubMed1988

The relationship between inhibition of plasminogen-activator activity and prostatic involution.

The role of plasminogen activators (PAs) as potential mediators of involution of the rat ventral prostate was investigated by using an approach involving the administration in vivo of anti-PA drugs. The prostates of castrated rats, which had been injected daily for 7 days with the anti-PA drugs 6-aminohexanoic acid, tranexamic acid, aprotinin and cortisol, were assayed for PA activity, weight and cell number. In the prostates from the castrated controls, there was a 10-fold increase in the mean PA activity and a 7-fold decrease in cell number relative to that of the non-castrated animals. Although this rise in enzyme activity could be decreased to some extent by all the drugs except aprotinin, only treatment with high doses of tranexamic acid or cortisol had a statistically significant effect. A similar pattern was observed with respect to the relative potency of the drugs in preventing the loss of prostatic weight and cell number after castration. The effects of cortisol were dose-dependent, with complete inhibition of both the rise in PA activity and cell loss occurring at a dose of about 15 mg/day. Since the concentration of the principal intranuclear androgen, dihydrotestosterone, was the same in the prostates from treated and untreated castrated rats, the effects of cortisol are not due to increased retention of this androgen. Rather, the high inverse correlation (r = 0.86) between the cellular concentration of PA activity and the cell population of the prostate implies that PAs are directly associated with prostatic involution and that cortisol, and to a lesser extent tranexamic acid, blocks the involution process through inhibition of PAs.

Aminocaproates↗