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L Mueller

Publications and source records attributed to L Mueller.

At least 55 records · Page 3Linked to original sources
PubMed1996

The three-dimensional solution structure of the SH2 domain from p55blk kinase.

Signal transduction in B cells is mediated, in part, by the interaction of the cytoplasmic components of the antigen receptor complex and various members of the src family tyrosine kinases. Key to this process appears to be the interaction of the tyrosine kinase SH2 domains with the tyrosine-phosphorylated cytoplasmic domain of Ig-alpha, a disulfide-bonded heterodimeric (with Ig-beta or Ig-gamma) transmembrane protein that noncovalently associates with the antigen receptor immunoglobin chains. In addition to binding to the phosphorylated cytoplasmic domains of Ig-alpha and Ig-beta, blk and fyn(T), two members of the src family kinases, have been shown to bind overlapping but distinct sets of phosphoproteins [Malek & Desiderio (1993) J. Biol. Chem. 268. 22557-22565]. A comparison of their three-dimensional structures may elucidate the apparently subtle differences required for phosphoprotein discrimination. To begin characterizing the blk/fyn/phosphosphoprotein interactions, we have determined the three-dimensional solution structure of the SH2 domain of blk kinase by nuclear magnetic resonance (NMR) spectroscopy. 1H, 13C, and 15N resonances of the SH2 domain of blk kinase were assigned by analysis of multidimensional, double- and triple-resonance NMR experiments. Twenty structures of the blk SH2 domain were refined with the program X-PLOR using a total of 2080 experimentally derived conformational restraints. The structures converged to a root-mean-squared (rms) distance deviation of 0.51 and 0.95 A for the backbone atoms and for the non-hydrogen atoms, respectively. The blk SH2 domain adopts the prototypical SH2 fold. Structurally, blk SH2 is most similar to the crystal structure of the v-src SH2 domain [Waksman et al. (1993) Nature 358.646-653] and superimposes on the crystal structure with an rmsd of 1.52 A for the backbone atoms. The largest deviations occur in the four loops interconnecting beta-strands A-E, which are the least well-defined regions in the NMR structure. Exclusion of these loops lowers this rmsd to 0.82 A. The conformation of the BC loop in the blk SH2 domain is similar to the open conformation in the apo lck SH2 domain, suggesting that, like the lck SH2 domain, the blk SH2 domain may have a gated phosphopeptide binding site. Finally, it is proposed that the amino acid substitution of Lys 88 (blk) for Glu [fyn(T)] is important for the observed differences in specificity between blk and fyn(T) SH2 domains.

Amino Acid Sequence↗
PubMed1996

Correlation of the guanosine exchangeable and nonexchangeable base protons in 13C-/15N-labeled RNA with an HNC-TOCSY-CH experiment.

A triple resonance HNC-TOCSY-CH experiment is described for correlating the guanosine imino proton and H8 resonances in 13C-/15N-labeled RNAs. Sequential assignment of the exchangeable imino protons in Watson-Crick base pairs is generally made independently of the assignment of the nonexchangeable base protons. This H(NC)-TOCSY-(C)H experiment makes it possible to unambiguously link the assignment of the guanosine H8 resonances with sequential assignment of the guanosine imino proton resonances. 2D H(NC)-TOCSY-(C)H spectra are presented for two isotopically labeled RNAs, a 30-nucleotide lead-dependent ribozyme known as the leadzyme, and a 48-nucleotide hammerhead ribozyme-RNA substrate complex. The results obtained on these two RNAs demonstrate that this HNC-TOCSY-CH experiment is an important tool for resonance assignment of isotopically labeled RNAs.

Base Sequence↗
PubMed1996

Analgesic use in cluster headache.

Cluster headache is a brutal affliction characterized by excruciating pain with relatively brief, but frequent attacks. Because of the short duration of the attacks and the tremendous intensity of pain, symptomatic analgesics are often not effective. However, inhalation oxygen, while being cumbersome, is reported to be effective in the majority of sufferers. To assess the practical effectiveness and use of analgesics and/or oxygen, a review of 60 cluster patients was conducted. At initial evaluation, 48 patients had accepted oral analgesics and 51 patients accepted inhalation oxygen for breakthrough headaches. After acceptable prophylactic treatment was established, 65% of patients who accepted analgesics continued their use, although most reported only minimal relief. Only 31% of patients who accepted oxygen continued its use, in spite of the fact that most sufferers reported significant relief. From this brief study, it appears that cluster headache patients prefer to use analgesics for reasons that are not solely for relief of pain, and that patients decline the use of oxygen for reasons other than lack of effectiveness.

Adult↗
PubMed1996

Vasospasm-induced myocardial infarction with sumatriptan.

Sumatriptan, a 5-hydroxytryptamine1, (5-HT1) receptor agonist is an effective abortive agent for migraine headaches. A common side effect in 3% to 7.9% of patients is chest pain. Although most cases of chest pain are not thought to be of cardiac origin, its mechanism is not entirely understood. Rare examples of electrocardiogram changes consistent with transient ischemia have been reported. Isolated instances of angina, arrhythmia, myocardial infarction, and death have been temporally associated with sumatriptan administration. In most cases, it is unclear whether underlying cardiovascular disease existed or contributed to this adverse event. We report the history of a 56-year-old female patient with migraine who experienced a myocardial infarction shortly after using sumatriptan, despite having had a normal cardiovascular evaluation. As she had a normal cardiac catheterization after the event, we find it probable that sumatriptan induced coronary vasospasm and myocardial infarction.

Coronary Vasospasm↗
PubMed1996

Time-related induction of DNA repair synthesis in rat hepatocytes following in vivo treatment with cyproterone acetate.

Cyproterone acetate (CPA), a synthetic steroid hormone widely used as a human pharmaceutical, has recently been shown to induce unscheduled DNA synthesis (UDS) in vitro in primary cultures of rat and human hepatocytes. In the present study CPA was evaluated for its ability to initiate UDS in the liver of female rats in vivo by means of the in vivo/in vitro hepatocyte DNA repair test. Using the standard sampling time of 16 h after single oral dosing, a dose-related UDS response at >50 mg CPA/kg body wt was observed. In order to examine the time course of CPA-induced UDS, different sampling times (4, 16, 48, 72, 96 and 144 h) after a single oral administration of 100 mg CPA/kg body wt were used. Whereas no UDS was induced in liver cells isolated 4 h after treatment, continuous DNA repair activity was observed after 16 h, with a maximum effect of approximately 10 net nuclear grains on day 4 after dosing. After a post-application period of 6 days the net grain counts returned to near control level. In contrast to the data with CPA, DNA damage induced by the positive control compound 2-acetylaminofluorene was removed much faster, within 2 days after administration. The time course of UDS activity during the first 4 days after administration of CPA parallels the previously reported time course of DNA adduct formation. However, a subsequent decrease and final cessation of UDS on day 6 takes place, although significant levels of CPA-DNA adducts have been reported to occur at that time point in rat liver cells. Whereas the time-related onset of UDS is suggested to reflect the pharmacokinetics of the activation of CPA to DNA-reactive intermediates, it remains unclear why the excision repair of DNA adducts did not continue. In addition to DNA repair synthesis, CPA was also shown to clearly increase the incidence of S phase cells under the test conditions applied, confirming the known mitogenic potential of CPA in rat liver.

Androgen Antagonists↗
PubMed1996

A pseudopeptide incorporating the tetrahydrophthalazine nucleus, a constrained aza analog of phenylalanine.

Replacement of the alpha-carbon with a nitrogen in alpha-amino acids gives rise to azaamino acids. Most examples of azaamino acids that have been incorporated into peptides are linear analogs, in which conformational effects are restricted to the immediate vicinity of the urea bond. In contrast to the linear azaamino acids, the heterocyclic analogs might be expected to exhibit stronger conformational preferences, but examples of this class of azaamino acids are very limited. We synthesized tetrahydrophthalazine (THPhth) as a constrained phenylalanine analog and elaborated it into the model pseudotripeptide N-¿([N-alanyl]-1,2,3,4-tetrahydro-2-phthalazinyl)carbonyl)¿-L-alan ine (1). As shown by NMR studies, tetrahydrophthalazine 1A has a secondary structure in which psi THphth is fixed at 16-18 degrees and there are two equal populations of cis and trans amide bonds from the N-terminal alanine.

Magnetic Resonance Spectroscopy↗
PubMed1996

Birth-weight percentiles by gestational age, Connecticut 1988-1993.

Extreme birth weights are associated with increased infant mortality and morbidity. Identifying infants of extreme birth weight is important for both clinical assessment and public health research. This study aimed to produce charts of birth-weight percentiles by gestational age for male and female, black and white infants in Connecticut. Data were obtained from registrations of live births to Connecticut residents in Connecticut, 1988-1993. During this period 263,032 births were registered to black and white women. Birth weight was missing in only 90 records but gestational age was missing in 29,865 (11%) records. An additional 0.5% of births were excluded because the recorded birth weight was an extreme outlier for the recorded gestational age. Birth records with missing gestational age had lower mean birth weights and proportionately more births < or = 1500 g when compared to birth records where gestation was reported; however the magnitude of the differences was small. Our charts provide population-based birth-weight percentiles by gestational age based on the most recent Connecticut birth data available. They are the most appropriate population norms available for Connecticut clinicians and researchers.

Birth Weight↗
PubMed1995

Predictors of groin complications after balloon and new-device coronary intervention.

We reviewed the clinical course of 5,042 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) using balloons or new devices: (stent, laser, directional and rotational atherectomy). A vascular complication was defined as the formation of a groin hematoma, bleeding, pseudoaneurysm, fistula, or the need for surgical repair. Vascular complications occurred in 309 (6.1%) patients, and 117 (2.3%) required vascular repair; among these patients, surgery was performed for correction of an an arteriovenous fistula in 12%, repair of pseudoaneurysm in 72%, repair for expanding hematoma and femoral artery lacerations in 10%, and retroperitoneal bleeding in 6%. The correlates of vascular complications were older age (66.8 vs 62.1 years; p < 0.0001), female gender (43% vs 26%; p < 0.0001), increased weight (82.1 +/- 16.46 vs 78.0 +/- 16.6 kg; p < 0.001), higher systolic blood pressure (140 +/- 25 vs 134 +/- 20 mm Hg; p < 0.001), increased heparin dose during the procedure (14,352 +/- 3,879 vs 13,599 +/- 3,508 IU; p = 0.001), administration of heparin after the procedure (232 vs 2,985 patients; p < 0.0001) and intracoronary stenting (14.9% vs 3.5%; p < 0.0001). Fifteen patients of 214 (7.0%) who underwent stent implantation had surgical repair. Vascular complications were not related to the size of the arterial sheath (8.11 +/- 0.8 vs 8.8 +/- 0.7Fr; p = 0.11) and the use of devices other than stents (laser, atherectomy) did not increase the rate of vascular complications.

Aged↗
PubMed1995

Refined solution structure of human profilin I.

Profilin is a ubiquitous eukaryotic protein that binds to both cytosolic actin and the phospholipid phosphatidylinositol-4,5-bisphosphate. These dual competitive binding capabilities of profilin suggest that profilin serves as a link between the phosphatidyl inositol cycle and actin polymerization, and thus profilin may be an essential component in the signaling pathway leading to cytoskeletal rearrangement. The refined three-dimensional solution structure of human profilin I has been determined using multidimensional heteronuclear NMR spectroscopy. Twenty structures were selected to represent the solution conformational ensemble. This ensemble of structures has root-mean-square distance deviations from the mean structure of 0.58 A for the backbone atoms and 0.98 A for all non-hydrogen atoms. Comparison of the solution structure of human profilin to the crystal structure of bovine profilin reveals that, although profilin adopts essentially identical conformations in both states, the solution structure is more compact than the crystal structure. Interestingly, the regions that show the most structural diversity are located at or near the actin-binding site of profilin. We suggest that structural differences are reflective of dynamical properties of profilin that facilitate favorable interactions with actin. The global folding pattern of human profilin also closely resembles that of Acanthamoeba profilin I, reflective of the 22% sequence identity and approximately 45% sequence similarity between these two proteins.

Actins↗
PubMed1995

Characterization of a new four-chain coiled-coil: influence of chain length on stability.

Limited information is available on inherent stabilities of four-chain-coils. We have developed a model system to study this folding motif using synthetic peptides derived from sequences contained in the tetramerization domain of Lac repressor. These peptides are tetrameric as judged by both gel filtration and sedimentation equilibrium and the tetramers are fully helical as determined by CD. The four-chain coiled-coils are well folded as judged by the cooperativity of thermal unfolding and by the extent of dispersion in aliphatic chemical shifts seen in NMR spectra. In addition, we measured the chain length dependence of this four-chain coiled-coil. To this end, we developed a general procedure for nonlinear curve fitting of denaturation data in oligomeric systems. The dissociation constants for bundles that contain alpha-helical chains 21, 28, and 35 amino acids in length are 3.1 x 10(-12), 6.7 x 10(-23), and 1.0 x 10(-38) M3, respectively. This corresponds to tetramer stabilities (in terms of the peptide monomer concentration) of 180 microM, 51 nM, and 280 fM, respectively. Finally, we discuss the rules governing coiled-coil formation in light of the work presented here.

Amino Acid Sequence↗
PubMed1995

Triple resonance HNCCCH experiments for correlating exchangeable and nonexchangeable cytidine and uridine base protons in RNA.

A set of triple resonance experiments is presented, providing through-bond H2N/HN to H6 connectivities in uridines and cytidines in 13C-/15N-labeled RNAs. These connectivities provide an important link between the sequential assignment pathways for the exchangeable and nonexchangeable proton resonances in nucleic acids. Both 2D and pseudo-3D HNCCCH experiments were applied to a 30-nucleotide lead-dependent ribozyme, known as the leadzyme. The HN to H6 connectivities for three uridines in the leadzyme were identified from one 2D H(NCCC)H experiment, and the H2N to H6 connectivities were identified for seven of the eight cytidines from the combination of a 2D H(NCCC)H and a pseudo-3D H(NCC)CH experiment.

Animals↗
PubMed1995

In vitro mutagenicity studies on cyproterone acetate using female rat hepatocytes for metabolic activation and as indicator cells.

The synthetic sex steroid cyproterone acetate (CPA) was shown to induce DNA repair in primary hepatocytes from female rats, confirming previous reports about a sex-specific genotoxic potential of CPA in female rat liver. CPA did not induce gene mutations or chromosomal aberrations in V79 Chinese hamster cells co-cultivated with hepatocytes from female rats as the metabolizing system. Hepatocytes from the same rats under identical exposure conditions as in the positive unscheduled DNA synthesis (UDS) test were used in these experiments. The maximum concentrations tested in the mutagenicity assays were 30-100 times higher compared with the lowest observed effect concentration of 3 x 10(-6) mol/l in the DNA repair test. The requirement for cell-cell transfer of the putative genotoxic metabolites in the co-culture experiments may be the reason for the discrepancy between positive UDS effects and negative mutagenicity and clastogenicity results. To further investigate if CPA can induce chromosomal mutations within the same cells that provide metabolic activation an in vitro micronucleus assay with proliferating female rat hepatocytes was performed. The results gave some indications of a micronucleus-inducing potential of CPA. However, under the conditions of the micronucleus assay CPA was also shown to increase the proliferative activity of hepatocytes. Since micronucleus formation is also dependent on mitotic activity, it cannot be determined whether the increase in micronucleus formation after CPA exposure indicates a clastogenic potential or whether it is just a consequence of the mitogenic potential of CPA. Although CPA or its metabolites obviously have a DNA damaging potential and stimulate considerable DNA excision repair, our findings do not establish a clear mutagenic potential.

Animals↗
PubMed1995

Family-centered/interdisciplinary team approach to working with families of children who have mental retardation.

Working with children who have mental retardation and their families is challenging and rewarding. When these children also have behavioral/psychiatric problems, the challenge is far greater. An interdisciplinary team is needed for comprehensive assessment, treatment, and management in order to be successful in accomplishing goals, providing continuity of care, and supporting the family in the community. In this paper we focused on the interdisciplinary team concept blended with the family-centered approach in a psychiatric setting and provided a case study of a family who had a child diagnosed with mental retardation, autism, and severe behavior problems. Practical suggestions were given to demonstrate the implementation of a family-centered/interdisciplinary team approach.

Adolescent↗
PubMed1994

Orientation of peptide fragments from Sos proteins bound to the N-terminal SH3 domain of Grb2 determined by NMR spectroscopy.

NMR spectroscopy has been used to characterize the protein-protein interactions between the mouse Grb2 (mGrb2) N-terminal SH3 domain complexed with a 15-residue peptide (SPLLPKLPP-KTYKRE) corresponding to residues 1264-1278 of the mouse Sos-2 (mSos-2) protein. Intermolecular interactions between the peptide and 13C-15N-labeled SH3 domain were identified in half-reverse-filtered 2D and 3D NOESY experiments. Assignments for the protons involved in interactions between the peptide and the SH3 domain were confirmed in a series of NOESY experiments using a set of peptides in which different leucine positions were fully deuterated. The peptide ligand-binding site of the mGrb2 N-terminal SH3 domain is defined by the side chains of specific aromatic residues (Tyr7, Phe9, Trp36, Tyr52) that form two hydrophobic subsites contacting the side chains of the peptide Leu4 and Leu7 residues. An adjacent negatively charged subsite on the SH3 surface is likely to interact with the side chain of a basic residue at peptide position 10 that we show to be involved in binding. The peptide-binding site of the SH3 is characterized by large perturbations of amide chemical shifts when the peptide is added to the SH3 domain. The mGrb2 N-terminal SH3 domain structure in the complex is well-defined (backbone RMSD of 0.56 +/- 0.21 calculated over the backbone N, C alpha, and C atoms of residues 1-54). The structure of the peptide in the complex is less well-defined but displays a distinct orientation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptor Proteins, Signal Transducing↗
PubMed1994

Solution structure of an isolated antibody VL domain.

The solution structure of the isolated VL domain of the anti-digoxin antibody 26-10 has been determined using data derived from heteronuclear multi-dimensional nuclear magnetic resonance (n.m.r.) experiments. Analytical ultracentrifugation and n.m.r. data demonstrate that the VL domain is only weakly associating (Kd = 2.5 (+/- 0.7) mM) and that it experiences a rapid monomer/dimer equilibrium under the n.m.r. experimental conditions. Therefore, the results reported here represent the first structure determination of an antibody VL domain in the absence of fixed quaternary interactions. The structure determination is based on 930 proton-proton distance constraints, 113 dihedral angle constraints, and 46 hydrogen bond constraints. Eighty initial structures were calculated with the variable target function program DIANA; of these, 31 were accepted on the basis of satisfaction of constraints (no distance constraint violations > 0.5 A; target function < 3.0 A2). Accepted DIANA structures were refined by restrained energy minimization using the X-PLOR program. The 15 best energy-minimized DIANA structures were chosen as a representative ensemble of solution conformations. The average root-mean-square differences (r.m.s.d.) between the individual structures of this ensemble and the mean coordinates is 0.85 (+/- 0.10) A for all backbone atoms and 1.29 (+/- 0.10) A for all heavy atoms. For beta-strands A, B, C, D, E and F, the average backbone atom r.m.s.d. to the mean structure is 0.46 (+/- 0.06) A. A higher-resolution ensemble, with all backbone atom and all heavy atom r.m.s.d.s. to the mean coordinates of 0.54 (+/- 0.08) A and 0.98 (+/- 0.12) A, respectively, was obtained by X-PLOR simulated annealing refinement of the 15 energy-minimized DIANA structures. A detailed analysis of the original ensemble of 15 energy-minimized DIANA structures is presented, as this ensemble retains a broader, and possibly more realistic, sampling of conformation space. The backbone atom and all heavy atom r.m.s.d.s between the mean energy-minimized DIANA structure and the X-ray derived coordinates of the VL domain within the Fab/digoxin complex are 1.05 A and 1.56 A, respectively. Subtle differences between the solution and X-ray structures occur primarily in CDR2, CDR3, beta-strands A, F and G, and localized regions of hydrophobic packing. Overall, these results demonstrate that the 26-10 VL domain conformation is determined primarily by intradomain interactions, and that quaternary VL-VH association induces relatively minor conformational adjustments.

Computer Graphics↗