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PubMed2006

Role of aspartic acid in collagen structure and stability: A molecular dynamics investigation.

A molecular dynamics (MD) simulation study has been carried out to understand the stability of the triple helical collagen models. The calculations show that the presence of the aspartic acid residue in different positions leads to the local variation in the structure. Analyses of root-mean-square deviation (RMSD), radial distribution function (RDF), puckering effect, dihedral angle variation, hydrogen bond (H-bond), and conformational changes during molecular dynamics simulation reveal that the local perturbation in the sequences, increase in chain flexibility due to removal of five membered rings in the collagen by aspartic acid, change of intermolecular H-bonding pattern, and differences in the association of water are mainly influencing the nature of stabilization of collagen by aspartic acid.

Amino Acid Sequence↗
PubMed1977

[Teratogenic effect of N-phthaloyl-L-aspartic acid on the mouse (author's transl)].

The optical isomers of N-phthaloyl-aspartic acid, structurally related to thalidomide, were administered i.p. to pregnant mice on day 9 of gestation; the injected solutions contained Tween 20 as solubilizer. N-Phthaloyl-L-aspartic acid exerts an embryotoxic and teratogenic effect as is evident by the high incidence of resorption and malformations. On the other hand the D-isomer is devoid of any embryotoxic and teratogenic activity under the same conditions of experiment.

Animals↗
PubMed1982

L-Aspartic acid induces a region of negative slope conductance in the current-voltage relationship of cultured spinal cord neurons.

Individual murine spinal cord neurons were grown in dissociated tissue cultures. Using either one or two conventional intracellular microelectrodes neurons were voltage-clamped and current-voltage (I-V) curves were constructed using command pulses. L-Aspartic acid was then applied and I-V curves repeated in the presence of this excitatory amino acid. L-Aspartic acid induced a region of negative slope conductance (RNSC) in the steady-state I-V relationships of these neurons. Such a RNSC accounts for the apparent reduction of conductance in response to excitatory amino acids and its instability likely contributes to the electrogenesis of bursting in central neurons.

Animals↗
PubMed1986

Age-dependent accumulation of protein residues which can be hydrolyzed to D-aspartic acid in human erythrocytes.

We have measured the rate of accumulation of amino acid residues in human erythrocyte membrane and cytosolic proteins which give D-aspartic acid upon acid hydrolysis. These residues would include D-aspartic acid, D-asparagine, as well as the beta-transpeptidation product, D-isoaspartic acid. Measurements made using age (density) fractionated cells indicate that racemization at these residues occurs on membrane proteins with a t1% (the time required to convert 1% to the D configuration) of about 38.6 days. Fractionation of membrane components revealed a faster rate of racemization for intrinsic proteins than for extrinsic proteins. On the other hand, significant age-dependent racemization was not detected for cytosolic proteins, and the calculated t1% value for these proteins is at least 4 times larger. These results suggest that in the 120-day life span of an erythrocyte, significant racemization of membrane (but not cytosolic) proteins can occur. We have also determined that the rates of accumulation of these residues for erythrocyte membrane and cytosolic proteins incubated in vitro are similar to those observed in vivo. These observations are discussed in terms of the possible cellular metabolism of racemized proteins.

Asparagine↗
PubMed1984

Increased concentrations of aspartic acid in the cerebrospinal fluid of patients with epilepsy and trigeminal neuralgia: an effect of medication?

The concentrations of free amino acids in the cerebrospinal fluid (CSF) were quantitated in 14 patients with epilepsy, 7 patients with trigeminal neuralgia, 10 patients with various neurological diseases and in 30 apparently healthy individuals. In the CSF of patients with epilepsy, the mean concentrations of aspartic acid (Asp), glutamine (Gln), histidine and phosphoserine were significantly higher than in the healthy individuals. The mean concentration of aspartic acid was higher in the patients on antiepileptic drug (AED) therapy than in the patients without AED therapy. The patients with trigeminal neuralgia had significantly increased CSF-concentrations of aspartic acid, glutamine and phosphoserine as compared to healthy individuals. Some patients receiving AED showed increased concentration of gamma-amino-butyric-acid (GABA).

Adolescent↗
PubMedDate not supplied

[Synthesis of L-aspartic acid by Escherichia coli and Pseudomonas fluorescens as related to the cultivation conditions].

The capacity of the cultures Escherichia coli str. 85, 113, BC, C and K-12 and Pseudomonas fluorescens str. 1 to synthesize L-aspartic acid from fumarate and ammonium ions was studied. E. coli str. 85 was shown to synthesize the largest amounts of aspartic acid. The cultivation conditions which helped to increase the activity several times were selected. The product of fumarate amination by ammonium ions was identified and found to be L-isomer of aspartic acid with an angle of rotation of [alpha] 20/D = +25,5 degrees in 6 N HCl.

Aspartic Acid↗
PubMed2002

Individual acid aspartic proteinases (Saps) 1-6 of Candida albicans are not essential for invasion and colonization of the gastrointestinal tract in mice.

In order to investigate whether there is a role for individual secreted aspartic proteinases (Saps) of Candida albicans in gastrointestinal infection of mice we compared the differential expression of SAP1-6 genes and production of Sap1-6 proteins with invasion and persistence of SAP knockout strains in the gastrointestinal tract. Using an in vivo expression technology (IVET) we found a high percentage of expression of SAP4-6 genes which increased steadily in the course of infection. Expression of SAP1-3 genes was detected occasionally and in lower percentages than that of SAP4-6 genes. With reverse transcriptase-polymerase chain reaction (RT-PCR), mRNA for SAP 4 and SAP6 were detected in the stomach of all mice, whereas SAP2, SAP3 and SAP5 mRNA were detected not in all animals and SAP1 mRNA was not detectable. Also with immunoelectron microscopy we demonstrated production of Saps1-3 as well as Saps4-6 with antibodies cross-reacting with either Saps1-3 or Saps4-6. In contrast to the fact that gene expression and production of Saps were readily detectable, we were unable to demonstrate differences in the ability to invade the stomach, to disseminate to the brain as well as in the duration of faecal shedding and the number of fungi persisting in the faeces of mice infected with SAP knockout strains in comparison to control strains. We conclude that although Saps were produced, individual Saps were not indispensable factors for virulence during gastrointestinal infection of mice.

Animals↗
PubMed1992

Substitution of lysine-181 to aspartic acid in the third transmembrane region of the endothelin (ET) type B receptor selectively reduces its high-affinity binding with ET-3 peptide.

In the G protein-coupled receptor family, a highly conserved aspartic acid located within the third transmembrane domain has been shown to be involved in ligand binding. Within the endothelin (ET) peptide receptor family, this aspartic acid has been replaced by a lysine. To assess the importance of this residue in ET binding, the lysine (position 181) of rat ET type B receptor was replaced by an aspartic acid. The effects on ligand binding and phosphoinositide turnover of both the wild-type and K181D mutant receptors were examined using transient receptor expression in COS-7 cells. Using [125I]ET-1 as the radioactive peptide ligand in displacement binding studies, the wild-type receptor displayed a typical non-isopeptide-selective binding profile with similar IC50 values (0.2-0.6 nM) for all three ET peptides (ET-1, ET-2, and ET-3). The mutant receptor showed an increase in IC50 values for ET-1 (5 nM), ET-2 (27 nM), and ET-3 (127 nM). The K181D mutant receptor still elicited full inositol phosphate (IP) accumulation responses in the presence of saturating concentrations of ETs (10 nM of ET-1, 100 nM of ET-2, or 1 microM of ET-3), indicating that the mutation did not affect G protein coupling.

Animals↗
PubMed1973

Racemization reaction of aspartic Acid and its use in dating fossil bones.

In the time interval datable by radiocarbon, and at the temperatures of most archeological sites, a substantial amount of racemization of aspartic acid takes place. By determination of the amount of racemization of aspartic acid in bones from a particular location which have been dated by the radiocarbon technique, it is possible to calculate the in situ first-order rate constant for interconversion of the L- and D enantiomers of aspartic acid. Once this "calibration" has been calculated, the reaction can be used to date other bones from the deposit that are either too old to be dated by radiocarbon or that are too small for radiocarbon dating. The only assumption required with this approach is that the average temperature experienced by the "calibration" sample is representative of the average temperature experienced by older samples. This "calibration" technique is used herein to date bones from the Olduvai Gorge area in Tanzania, Africa.

Journal Article↗
PubMed2003

The l-isomer-selective transport of aspartic acid is mediated by ASCT2 at the blood-brain barrier.

Aspartic acid (Asp) undergoes l-isomer-selective efflux transport across the blood-brain barrier (BBB). This transport system appears to play an important role in regulating l- and d-Asp levels in the brain. The purpose of this study was to identify the responsible transporters and elucidate the mechanism for l-isomer-selective Asp transport at the BBB. The l-isomer-selective uptake of Asp by conditionally immortalized mouse brain capillary endothelial cells used as an in vitro model of the BBB took place in an Na+- and pH-dependent manner. This process was inhibited by system ASC substrates such as l-alanine and l-serine, suggesting that system ASC transporters, ASCT1 and ASCT2, are involved in the l-isomer selective transport. Indeed, l-Asp uptake by oocytes injected with either ASCT1 or ASCT2 cRNA took place in a similar manner to that in cultured BBB cells, whereas no significant d-Asp uptake occurred. Although both ASCT1 and ASCT2 mRNA were expressed in the cultured BBB cells, the expression of ASCT2 mRNA was 6.7-fold greater than that of ASCT1. Moreover, immunohistochemical analysis suggests that ASCT2 is localized at the abluminal side of the mouse BBB. These results suggest that ASCT2 plays a key role in l-isomer-selective Asp efflux transport at the BBB.

Amino Acid Transport System ASC↗
PubMed1988

1H-NMR studies of synthetic peptide analogues of calcium-binding site III of rabbit skeletal troponin C: effect on the lanthanum affinity of the interchange of aspartic acid and asparagine residues at the metal ion coordinating positions.

The present work determines the contribution of liganding aspartic acid (Asp) residues, at the +X, +Y, and +Z metal ion coordinating positions, to the lanthanum(3+) (La3+) ion binding affinity of synthetic analogues of calcium-binding site III of rabbit skeletal troponin C. Eight 13-residue synthetic analogues were prepared by solid-phase synthesis; the primary sequences of these analogues represent all possible combinations having aspartic acid and asparagine at the +X, +Y, and +Z positions. High-field proton nuclear magnetic resonance (NMR) spectroscopy was used to monitor the binding of the La3+ ion to each of the analogues. Comparison of the chemical shift changes showed large variations in the magnitude of the shift; these were reflected in the La3+ ion association constants determined for each analogue. The association constants ranged from 9.1 x 10(2) M-1 to 2.5 x 10(5) M-1. It was observed that those analogues with the larger number of acidic residues to coordinate the La3+ ion yielded the higher association constants. The La3+ ion binding results demonstrate that the Asp residues at the positions of study contribute equally and in an additive manner to the association constant and that the presence of neighboring Asp residues at either the +X and +Y, the +Y and +Z, or the +X and +Y and +Z metal ion coordinating positions introduced dentate-dentate repulsion, which, acts as to detract from the La3+ ion association constant of the analogues.

Amino Acids↗
PubMed1996

Beta-methylthio-aspartic acid: identification of a novel posttranslational modification in ribosomal protein S12 from Escherichia coli.

Utilizing microscale chemical derivatization reactions and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we have identified a novel posttranslational modification of aspartic acid, beta-methylthio-aspartic acid. The modified residue is located at position 88 in ribosomal protein S12 from Escherichia coli, a phylogenetically conserved protein that has been implicated in maintaining translational accuracy of the ribosome.

Aspartic Acid↗
PubMed1994

Nanometric design of extraordinary hydrophobic-induced pKa shifts for aspartic acid: relevance to protein mechanisms.

Commonly a key element enabling proteins to function is an amino acid residue or residues with functional side chains having shifted pKa values. This article reports the results on a set of protein-based polymers (model proteins) that exhibit hydrophobic folding and assembly transitions, and that have been designed for the purpose of achieving large hydrophobic-induced pKa shifts by selectively replacing Val residues by Phe residues. The high molecular weight polypentapeptides, actually poly(tricosapeptides) with six varied pentamers in fixed sequence, were designed and synthesized to have the same amino acid compositions but different proximities between a single aspartic acid residue and 5 Phe residues per 30 residues. With the 5 Phe residues distal from the Asp residue, the observed pKa shift was 2.9 when compared to the Val-containing reference. With the 5 Phe residues within 1 nm of the Asp residue, the pKa shift was 6.2. This represents a free energy of interaction of 8 kcal/mole. To our knowledge, this is the largest pKa shift documented for an Asp residue in a polypeptide- or protein-water system. Data are reviewed that do not support the usual electrostatic arguments for pKa shifts of charge-charge repulsion and/or unfavorable ion self-energies arising from displacement of water by hydrophobic moieties, but rather the data are interpreted to indicate the presence of an apolar-polar repulsive free energy of hydration, which results from a potentially highly cooperative competition between apolar and polar species for hydration.

Amino Acid Sequence↗