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

Polarised infrared transmission and Raman spectra of betaine ortho-phosphoric acid crystal in temperature ranges 13-393 and 13-300 K, respectively are reported and discussed in relation to phase transitions: antiferrodistortive at T(c1) = 365 K and antiferroelectric at T(c3) = 81 K. The spectra are consistent with unit cell doubling below T(c3). The participation of all hydrogen bonds apparent in the crystal in the antiferroelectric phase transition was shown. Quite large freedom of -N(CH(3))(3) groups reorientation in the antiferroelectric phase was detected. No changes were found in the transmission spectra taken in the vicinity of the antiferrodistortive phase transition temperature.
Spectrochim Acta A Mol Biomol Spectrosc 2003 Mar 15
PMID:Polarised vibrational spectra of betaine ortho-phosphoric acid complex. Part II. Phase transitions studies. 1263 14

The FTIR spectra of pyridinium-betaine of squaric acid in 4000-100 cm(-1) frequency region in solid state were measured. In addition, the structure and harmonic vibrational frequencies of this molecule were theoretically evaluated using restricted Hartree-Fock and B3LYP density functional methods. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Comparison with the experimental spectra provides important information about the ability of these computational methods to describe the vibrational modes in these highly polar strained ring compounds.
Spectrochim Acta A Mol Biomol Spectrosc 2003 Jun
PMID:Experimental and computational studies of the structure and vibrational spectra of pyridinium-betaine of squaric acid. 1273 67

Active protein-disaggregation by a chaperone network composed of ClpB and DnaK + DnaJ + GrpE is essential for the recovery of stress-induced protein aggregates in vitro and in Escherichia coli cells. K-glutamate and glycine-betaine (betaine) naturally accumulate in salt-stressed cells. In addition to providing thermo-protection to native proteins, we found that these osmolytes can strongly and specifically activate ClpB, resulting in an increased efficiency of chaperone-mediated protein disaggregation. Moreover, factors that inhibited the chaperone network by impairing the stability of the ClpB oligomer, such as natural polyamines, dilution, or high salt, were efficiently counteracted by K-glutamate or betaine. The combined protective, counter-negative and net activatory effects of K-glutamate and betaine, allowed protein disaggregation and refolding under heat-shock temperatures that otherwise cause protein aggregation in vitro and in the cell. Mesophilic organisms may thus benefit from a thermotolerant osmolyte-activated chaperone mechanism that can actively rescue protein aggregates, correctly refold and maintain them in a native state under heat-shock conditions.
Mol Microbiol 2003 Jul
PMID:Dicarboxylic amino acids and glycine-betaine regulate chaperone-mediated protein-disaggregation under stress. 1282 38

Early nutrition affects adult metabolism in humans and other mammals, potentially via persistent alterations in DNA methylation. With viable yellow agouti (A(vy)) mice, which harbor a transposable element in the agouti gene, we tested the hypothesis that the metastable methylation status of specific transposable element insertion sites renders them epigenetically labile to early methyl donor nutrition. Our results show that dietary methyl supplementation of a/a dams with extra folic acid, vitamin B(12), choline, and betaine alter the phenotype of their A(vy)/a offspring via increased CpG methylation at the A(vy) locus and that the epigenetic metastability which confers this lability is due to the A(vy) transposable element. These findings suggest that dietary supplementation, long presumed to be purely beneficial, may have unintended deleterious influences on the establishment of epigenetic gene regulation in humans.
Mol Cell Biol 2003 Aug
PMID:Transposable elements: targets for early nutritional effects on epigenetic gene regulation. 1286 Oct 15

The PAT family of proton-dependent amino acid transporters has recently been identified at the molecular level. This paper describes the structural requirements in substrates for their interaction with the cloned murine intestinal proton/amino acid cotransporter (PAT1). By using the Xenopus laevis oocytes as an expression system and by combining the two-electron voltage clamp technique with radiotracer flux studies, it was demonstrated that the aliphatic side chain of L-alpha-amino acids substrates can consist maximally of only one CH2-unit for high affinity interaction with PAT1. With respect to the maximal separation between the amino and carboxyl groups, only two CH2-units, as in gamma-aminobutyric acid (GABA), are tolerated. PAT1 displays no or even a reversed stereoselectivity, tolerating serine and cystein only in the form of D-enantiomers. A methyl-substitution of the carboxyl group (e.g. O-methyl-glycine) markedly diminishes substrate affinity and transport rates, whereas methyl-substitutions at the amino group (e.g. sarcosine or betaine) have only minor effects on substrate interaction with the transporter binding site. Furthermore, it has been shown (by kinetic analyses of radiolabelled betaine influx and inhibition studies) that the endogenous PAT system of human Caco-2 cells has very similar transport characteristics to mouse PAT1. In summary, one has defined the structural requirements and limitations thet determine the substrate specificity of PAT1. A critical recognition criterion of PAT1 is the backbone charge separation distance and the side chain size, whereas substitutions on the amino group are well tolerated.
Mol Membr Biol
PMID:Substrate recognition by the mammalian proton-dependent amino acid transporter PAT1. 1289 27

The symbiotic soil bacterium Sinorhizobium meliloti has the capacity to synthesize the osmoprotectant glycine betaine from choline-O-sulfate and choline. This pathway is encoded by the betICBA locus, which comprises a regulatory gene, betI, and three structural genes, betC (choline sulfatase), betB (betaine aldehyde dehydrogenase), and betA (choline dehydrogenase). Here, we report that betICBA genes constitute a single operon, despite the existence of intergenic regions containing mosaic elements between betI and betC, and betB and betA. The regulation of the bet operon was investigated by using transcriptional lacZ (beta-galactosidase) fusions and has revealed a strong induction by choline at concentrations as low as 25 microM and to a lesser extent by choline-O-sulfate and acetylcholine but not by osmotic stress or oxygen. BetI is a repressor of the bet transcription in the absence of choline, and a nucleotide sequence of dyad symmetry upstream of betI was identified as a putative betI box. Measurements of intracellular pools of choline, well correlated with beta-galactosidase activities, strongly suggested that BetI senses the endogenous choline pool that modulates the intensity of BetI repression. In contrast to Escherichia coli, BetI did not repress choline transport. During symbiosis with Medicago sativa, S. meliloti bet gene expression was observed within the infection threads, in young and in mature nodules. The existence of free choline in nodule cytosol, peribacteroid space, and bacteroids was demonstrated, and the data suggest that bet regulation in planta is mediated by BetI repression, as in free-living cells. Neither Nod nor Fix phenotypes were significantly impaired in a betI::omega mutant, indicating that glycine betaine biosynthesis from choline is not crucial for nodulation and nitrogen fixation.
Mol Plant Microbe Interact 2003 Aug
PMID:The Sinorhizobium meliloti glycine betaine biosynthetic genes (betlCBA) are induced by choline and highly expressed in bacteroids. 1290 15

Alcohol dehydrogenases (ADHs) of the MDR type (medium-chain dehydrogenases/reductases) have diverged into two evolutionary groups in eukaryotes: a set of 'constant' enzymes (class III) typical of basal enzymes, and a set of 'variable' enzymes (remaining classes) suggesting 'evolving' forms. The variable set has larger overall variability, different segment variability, and variability also in functional segments. Using a major aldehyde dehydrogenase (ALDH) from cod liver and fish ALDHs deduced from the draft genome sequence of Fugu rubripes (Japanese puffer fish), we found that ALDHs form more complex patterns than the ADHs. Nevertheless, ALDHs also group into 'constant' and 'variable' sets, have separate segment variabilities, and distinct functions. Betaine ALDH (class 9 ALDH) is 'constant,' has three segments of variability, all non-functional, and a limited fish/human divergence, reminiscent of the ADH class III pattern. Enzymatic properties of fish betaine ALDH were also determined. Although all ALDH patterns are still not known, overall patterns are related to those of ADH, and group separations may be distinguished. The results can be interpreted functionally, support ALDH isozyme distinctions, and assign properties to the multiplicities of the ADH and ALDH enzymes.
Cell Mol Life Sci 2003 Sep
PMID:Distinct but parallel evolutionary patterns between alcohol and aldehyde dehydrogenases: addition of fish/human betaine aldehyde dehydrogenase divergence. 1452 61

Haemophilus influenzae obtains choline from either its growth medium or host cell membrane lipids and expresses it on its lipopolysaccharide (LPS) in the form of phosphorylcholine (ChoP), which contributes to its pathogenesis by mimicry of host cell molecules. Two genes (licB and betT) revealed by whole genomic analysis as encoding potential choline transporters were tested for their role in LPS-ChoP synthesis. The betT gene in H. influenzae is similar to betT in Escherichia coli, which functions in choline transport for the generation of betaine in osmoprotection. The licB gene has homology to bacterial permeases including betT and is encoded in the lic1 locus, which is essential for the expression of LPS-ChoP. In the presence of high concentrations of choline, neither licB nor betT were necessary for expression of LPS-ChoP raising the possibility that other unidentified choline uptake mechanisms may exist in this species. However, under choline limiting conditions, including growth in human nasal airway surface fluid, the licB, but not betT, gene was required for choline transport and synthesis of LPS-ChoP suggesting that LicB functions as a high affinity choline permease. The betT, but not licB, gene was shown to function in osmoprotection in H. influenzae, similar to the role of betT in E. coli. Further analysis demonstrated growth condition dependent differences in the regulation of transcription of the licB and betT genes. We conclude that H. influenzae may have multiple mechanisms for choline uptake and distinct pathways for choline utilization in LPS-ChoP biosynthesis and osmoregulation.
Mol Microbiol 2003 Oct
PMID:Multiple mechanisms for choline transport and utilization in Haemophilus influenzae. 1461 77

The OpuA system of Bacillus subtilis is a member of the substrate-binding-protein-dependent ABC transporter superfamily and serves for the uptake of the compatible solute glycine betaine under hyperosmotic growth conditions. Here, we have characterized the nucleotide-binding protein (OpuAA) of the B.subtilis OpuA transporter in vitro. OpuAA was overexpressed heterologously in Escherichia coli as a hexahistidine tag fusion protein and purified to homogeneity by affinity and size exclusion chromatography (SEC). Dynamic monomer/dimer equilibrium was observed for OpuAA, and the K(D) value was determined to be 6 microM. Under high ionic strength assay conditions, the monomer/dimer interconversion was diminished, which enabled separation of both species by SEC and separate analysis of both monomeric and dimeric OpuAA. In the presence of 1 M NaCl, monomeric OpuAA showed a basal ATPase activity (K(M)=0.45 mM; k(2)=2.3 min(-1)), whereas dimeric OpuAA showed little ATPase activity under this condition. The addition of nucleotides influenced the monomer/dimer ratio of OpuAA, demonstrating different oligomeric states during its catalytic cycle. The monomer was the preferred species under post-hydrolysis conditions (e.g. ADP/Mg(2+)), whereas the dimer dominated the nucleotide-free and ATP-bound states. The affinity and stoichiometry of monomeric or dimeric OpuAA/ATP complexes were determined by means of the fluorescent ATP-analog TNP-ATP. One molecule of TNP-ATP was bound in the monomeric state and two TNP-ATP molecules were detected in the dimeric state of OpuAA. Binding of TNP-ADP/Mg(2+) to dimeric OpuAA induced a conformational change that led to the decay of the dimer. On the basis of our data, we propose a model that couples changes in the oligomeric state of OpuAA with ATP hydrolysis.
J Mol Biol 2003 Nov 28
PMID:Nucleotide dependent monomer/dimer equilibrium of OpuAA, the nucleotide-binding protein of the osmotically regulated ABC transporter OpuA from Bacillus subtilis. 1462 83

Bacteria respond to increasing medium osmolality by accumulating organic solutes that are compatible with cellular functions. Transporter ProP of Escherichia coli, a proton symporter and a member of the major facilitator superfamily, senses osmotic shifts and responds by importing osmolytes such as glycine betaine. ProP contains a cytoplasmic, C-terminal extension that is essential for its activity. A peptide corresponding to the C-terminal extension of ProP forms a homodimeric alpha-helical coiled-coil even though some of its heptad a positions are not occupied by hydrophobic amino acid residues. Unexpectedly, amino acid replacement R488I, occurring at a heptad a position, destabilized the coiled-coil formed by the ProP peptide and attenuated the response of the intact transporter to osmotic upshifts in vivo. Thus, ProP was proposed to dimerize via an antiparallel coiled-coil. We used nuclear magnetic resonance (NMR) spectroscopy to determine the structure of the synthetic peptide corresponding to residues 468-497 of ProP. This region did form an antiparallel coil-coil in which critical residue R488 specifies the antiparallel coiled-coil orientation by forming stabilizing salt-bridges. Charged residues (both acidic and basic) are clustered on the c/g surface of the coiled-coil whereas polar residues are distributed on the b/e surface. This causes the structure to be bent, in contrast to other known antiparallel coiled-coils (those from the hepatitis delta antigen (PDB ID code 1A92) and the bovine F(1) ATPase inhibitor protein (PDB ID code 1HF9)). The coiled-coil and its possible importance for osmosensing are discussed.
J Mol Biol 2003 Dec 12
PMID:Solution structure of the C-terminal antiparallel coiled-coil domain from Escherichia coli osmosensor ProP. 1464 66


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