Crystallization and preliminary X-ray diffraction analysis of monoprenylated Rab7 GTPase in complex with Rab escort protein 1

Posttranslational geranylgeranylation of Rab GTPases is catalyzed by Rab geranylgeranyltransferase (RabGGTase), which consists of a catalytic alpha/beta heterodimer and an accessory Rab escort protein (REP). REP functions as a molecular chaperone that presents Rab proteins to the RabGGTase and after prenylation delivers them to their target membrane. Mutations in the REP-1 gene in humans lead to an X-chromosome-linked defect known as choroideremia, a progressive disease that inevitably culminates in complete blindness. Here we report in vitro assembly, purification, and crystallization of the monoprenylated Rab7GDP:REP-1 complex. X-Ray diffraction data for the REP-1:Rab7 complex were collected to 2.2-A resolution at the ESRF. The crystals belong to the orthorhombic space group P2(1)2(1)2 with unit-cell parameters a=64.3A, b=105.3A, c=132.6A. Preliminary structural analysis revealed the presence of one complex in the asymmetric unit. To understand the conformational changes in Rab protein on complex formation we also crystallized the GDP-bound form of Rab7 that diffracted to at least 1.8A on the in-house X-ray source.     

Growth analysis in patients with 21-hydroxylase deficiency influence of glucocorticoid dosage,age at diagnosis,phenotype and genotype on growth and height outcome

OBJECTIVE: To evaluate the impact of hydrocortisone dosage, age at diagnosis, compliance, genotype and phenotype on growth and height outcome in 21-hydroxylase-deficient patients. METHODS: We analyzed 37 patients with 21-hydroxylase deficiency (17 had completed growth, 20 still growing). Final (FH)/predicted final height (pFH) and loss of height potential related to target height (TH) were calculated and the impact of 4 hydrocortisone (HC) dosage regimens on height outcome and growth velocities was evaluated. Mean FH SDS and pFH SDS were analyzed in accordance to age at diagnosis, compliance, genotype and phenotype. RESULTS: Mean (FH SDS, pFH SDS) was -1.8+/-1.06 SD, with 35.1% of all 37 patients exhibiting short stature. Doses >20 mg/m2/day during the first year and >15 mg/m2/day during age 1-5 and at puberty resulted in significantly lower FH SDS, pFH SDS and greater height losses. Age at diagnosis, compliance, genotype and phenotype played only a minor role in growth development. CONCLUSIONS: Hydrocortisone substitution in 21-hydroxylase-deficient patients should be kept at the lowest efficient level, if possible <20 during the first year and <15 mg/m2/day until age 5 and during puberty. Normal growth and not complete androgen suppression should be aimed for.     

Flavonoids from Achillea nobilis L

The detailed investigation of a methanolic extract of aerial parts of Achillea nobilis resulted in the isolation of 10 flavonoids. A new C-glycosylflavone, luteolin-6-C-apiofuranosyl-(1'-->2')-glucoside, was isolated besides orientin, isoorientin, vitexin, isoschaftoside, luteolin-7-O-beta-glucuronide, luteolin-4'-O-beta-glucoside and quercetin-3-O-methyl ether and two rare flavonolglycosides, quercetin-3-O-alpha-arabinosyl-(1'-->6')-glucoside and quercetin-3-O-methylether-7-O-beta-glucoside. The structures were established either by comparison with authentic substances or by UV, 1H NMR and 13C NMR spectroscopic methods including 2D-NMR techniques and ESI-MS.     

The DnaC helicase loader is a dual ATP/ADP switch protein

Helicases are transferred to replication origins by helicase loading factors. The Escherichia coli DnaC and eukaryotic Cdc6/18 helicase loaders contain ATP sites and are both members of the AAA+ family. One might expect that ATP is required for helicase loading; however, this study on DnaC illustrates that ATP is not actually needed for DnaC to load helicase onto single-strand DNA (ssDNA). In fact, it seems to be a paradox that after transfer of helicase to DNA, DnaC-ATP inhibits helicase action. In addition, ATP is required for DnaC function at an early step in oriC replication in which ATP stimulates ssDNA binding by DnaC, leading to expansion of the ssDNA bubble at the origin. Two cofactors, ssDNA and DnaB, trigger hydrolysis of ATP, converting DnaC to the ADP form that no longer inhibits DnaB. These observations have led to the idea that DnaC is a 'dual' switch protein, where both the ATP and the ADP forms are sequentially required for replication. This dual switching process may underlie the sensitivity of DnaB to even small fluctuations in DnaC levels.     

Localizing genes in Drosophila melanogaster polytene chromosomes by fluorescence in situ hybridization

This paper describes a method for the identification of single copy genes in Drosophila melanogaster polytene chromosomes, using fluorescence in situ hybridization (FISH). We demonstrate the detection of white (w) , a gene previously mapped to 1-1.5 region of the linkage map, and to 3C2 region of the cytogenetic map of X chromosome. Squash preparations of polytene chromosomes from salivary glands dissected out from third instar larvae of Drosophila melanogaster were denatured and subjected to hybridization with a digoxigenin labeled probe, corresponding to mini-white gene. The preparations were then washed and incubated with antidigoxigenin-fluorescein antibodies. After removal of the nonspecifically bound antibodies, the polytene chromosomes were counterstained with propidium iodide. Fluorescence microscopy revealed white locus in the X chromosome in a subterminal location, in agreement with the above mentioned maps. The protocol is efficient and adaptable for simultaneously multiple signal detection.     

Double transgenic mice with type 1 diabetes mellitus develop somatic, metabolic and vascular disorders

The double transgenic mice (dTg) were obtained by mating: (i) transgenic mice expressing the hemagglutinin of influenza virus under the insulin promoter with (ii) transgenic mice expressing specific T lymphocytes with receptor for the immunodominant epitope of the same virus. In this study we show that dTg mice developed type 1 diabetes mellitus associated with hyperglycemia, low level of plasma insulin, glucosuria, weight loss and approximately 90% mortality (at 3 months biological age). The membrane of red blood cells was more sensitive to osmotic shock in diabetic mice, compared to non-diabetic mice, assessing systemic oxidative stress. Both vasoconstriction and vasorelaxation of the renal arteries decreased significantly in diabetic mice (compared to the control group of non-diabetic mice) related to the phenotypic change of endothelium and smooth muscle cells within the artery wall. This animal model, may be used in developing various strategies to study pancreatic beta-cell function, as well as for a better metabolic control conducting to a reduced risk of vascular complications.     

Biodistribution of phosphodiester and phosphorothioate siRNA

Short interfering RNAs (siRNAs) are valuable tools for analyzing protein function in mammalian cell culture. This success has led to high expectations for in vivo and therapeutic applications. However, the pharmacokinetic properties of siRNA are not known. Here we report the biodistribution of a phosphodiester (PO) siRNA duplex and examine the effect of phosphorothioate (PS) linkages. Our findings indicate that biodistribution of siRNA is similar to that for single-stranded antisense oligonucleotides and offer insights for use of siRNA in vivo.     

Purification and kinetic characterization of recombinant human mitogen-activated protein kinase kinase kinase COT and the complexes with its cellular partner NF-kappa B1 p105

Cancer osaka thyroid (COT), a human MAP 3 K, is essential for lipopolysaccharide activation of the Erk MAPK cascade in macrophages. COT 30--467 is insoluble, whereas low levels of COT 30--397 can be expressed, but this protein is unstable. However, both COT 30--467 and COT 30--397 are expressed in a soluble and stable form when produced in complex with the C-terminal half of p105. The k(cat) of COT 30--397 is reduced approximately 47--fold in the COT 30--467/p105 Delta N complex. COT prefers Mn(2+) to Mg(2+) as the ATP metal cofactor, exhibiting an unusually high ATP K(m) in the presence of Mg(2+). When using Mn(2+) as the cofactor, the ATP K(m) is reduced to a level typical of most kinases. In contrast, the binding affinity of COT for its other substrate MEK is cofactor independent. Our results using purified proteins indicate that p105 binding improves COT solubility and stability while down-regulating kinase activity, consistent with cellular data showing that p105 functions as an inhibitor of COT.     

Role of regulatory F-domain in hepatocyte nuclear factor-4alpha ligand specificity

The F-domain of rat HNF-4alpha1 has a crucial impact on the ligand binding affinity, ligand specificity and secondary structure of HNF-4alpha. (i) Fluorescent binding assays indicate that wild-type, full-length HNF-4alpha (amino acids 1-455) has high affinity (Kd=0.06-12 nm) for long chain fatty acyl-CoAs (LCFA-CoA) and low affinity (Kd=58-296 nm) for unesterified long chain fatty acids (LCFAs). LCFA-CoA binding was due to close molecular interaction as shown by fluorescence resonance energy transfer (FRET) from full-length HNF-4alpha tryptophan (FRET donor) to bound cis-parinaroyl-CoA (FRET acceptor), which yielded an intermolecular distance of 33 A, although no FRET to cis-parinaric acid was detected. (ii) Deleting the N-terminal A-D-domains, comprising the AF1 and DNA binding functions, only slightly affected affinities for LCFA-CoAs (Kd=0.9-4 nm) and LCFAs (Kd=93-581 nm). (iii) Further deletion of the F-domain robustly reduced affinities for LCFA-CoA and reversed ligand specificity (i.e. high affinity for LCFAs (Kd=1.5-32 nm) and low affinity for LCFA-CoAs (Kd=54-302 nm)). No FRET from HNF-4alpha-E (amino acids 132-370) tryptophan (FRET donor) to bound cis-parinaroyl-CoA (FRET acceptor) was detected, whereas an intermolecular distance of 28 A was calculated from FRET between HNF-4alpha-E and cis-parinaric acid. (iv) Circular dichroism showed that LCFA-CoA, but not LCFA, altered the secondary structure of HNF-4alpha only when the F-domain was present. (v) cis-Parinaric acid bound to HNF-4alpha with intact F-domain was readily displaceable by S-hexadecyl-CoA, a nonhydrolyzable thioether analogue of LCFA-CoAs. Truncation of the F-domain significantly decreased cis-parinaric acid displacement. Hence, the C-terminal F-domain of HNF-4alpha regulated ligand affinity, ligand specificity, and ligand-induced conformational change of HNF-4alpha. Thus, characteristics of F-domain-truncated mutants may not reflect the properties of full-length HNF-4alpha.