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Biomedical subjects

D C Teller

Publications and source records attributed to D C Teller.

At least 37 records · Page 2Linked to original sources
PubMed1994

The corn inhibitor of blood coagulation factor XIIa. Crystallization and preliminary crystallographic analysis.

A 13.6 kDa protein from corn seeds is known to be a highly selective inhibitor of human blood coagulation Factor XIIa (or activated Hageman factor). We have crystallized this inhibitor at 23 degrees C and pH 7.5 from a solution of 30% polyethylene glycol 400, 0.2 M MgCl2, and 0.1 M Hepes. The crystals diffract to at least 2.1 A resolution. The space group is P4(2)2(1)2 with a = b = 57.15 A and c = 80.5 A. The crystals contain 51% solvent. Two heavy atom derivatives have been identified.

Cloning, Molecular↗
PubMed1994

Transglutaminase factor XIII uses proteinase-like catalytic triad to crosslink macromolecules.

The X-ray crystal structure of human transglutaminase factor XIII has revealed a cysteine proteinase-like active site involved in a crosslinking reaction and not proteolysis. This is among the first observations of similar active sites in 2 different enzyme families catalyzing a similar reaction in opposite directions. Although the size and overall protein fold of factor XIII and the cysteine proteinases are quite different, the active site and the surrounding protein structure share structural features suggesting a common evolutionary lineage. Here we present a description of the residues in the active site and the structural evidence that the catalytic mechanism of the transglutaminases is similar to the reverse mechanism of the cysteine proteinases.

Binding Sites↗
PubMed1993

Dynamics and structures of DNA: long-range effects of a 16 base-pair (CG)8 sequence on secondary structure.

The effects of inserting 16 base pair (bp) of alternating CG [(CG)8] near the middle of a much longer restriction fragment (1097 bp) are investigated by measuring various properties that are sensitive to secondary and tertiary structure. Results for this fragment are compared with those for a control fragment (1089 bp) with the identical sequence except at the insert. Another fragment (1382 bp), which contains a 296-bp extension at the 5'-end of the 1089-bp control fragment, is also used as a secondary control in some experiments. When the 1097-bp (CG)8 insert fragment is compared with the control fragments in 0.1 M NaCl buffer, the (CG)8 insert is found to induce disproportionately large relative changes in the molar ellipticity at 273 nm ([theta]273), the torsion constant (alpha) measured by fluorescence polarization anisotropy, the optical melting profile, and the susceptibility to S1 nuclease. Estimates of the minimum distance over which the (CG)8 insert alters the secondary structure range from 330 to 550 bp. With increasing NaCl concentration, the 1097-bp insert fragment undergoes a structural transition between 2.0 and 2.5 M that is manifested in the apparent diffusion coefficient (Dplat) from dynamic light scattering at large scattering vector. This transition, which is not exhibited by the control DNAs, is presumed to involve formation of Z-helix at the insert. However, the observed decrease in (Dplat) is attributed to an increase in bending rigidity, which perforce must be globally distributed far beyond the (CG)8 insert per se. In 4.25 M NaCl (but not in 0.1 M NaCl), the addition of 1 ethidium dye per 300 bp induces an extensive structural transition in the 1097 bp (CG)8 insert fragment. This transition, which also is not exhibited by the control DNAs, significantly decreases the bending rigidity, doubles [theta]273, and takes place on a time scale of a few days. Removal of ethidium and salt by dialysis vs 0.1 M NaCl buffer restores the original properties of the 1097-bp (CG)8 insert fragment. The present results are consistent with a (fluctuating, long-range) description of the secondary structure in which a given short sequence transiently fluctuates among two or more distinct secondary structures that extend over much larger domains of variable position and size, and whose relative stabilities depend on distant as well as close-lying base pairs.

Base Composition↗
PubMed1992

Periods of oscillatory growth in developing ocular lens correspond with cell cycle times.

Lens growth rates oscillated throughout neonatal rat lens development. Changes in weight, soluble protein content, and cell division were quantitatively analyzed between birth and 26 days of age. Fourier analysis of daily changes in total weight and soluble protein content identified reproducible periodicities of 50-57 hours. Shorter periodicities of 14-18 hours and 18-21 hours were found by analyzing changes in lens dry weight/6 hours and cell division/7 hours. Changes in dry weight and cell division also contained a second periodicity of 36 hours and 30-43 hours, respectively. The periods of observed oscillations corresponded to the length of stages of the lens epithelial cell cycle. Oscillating growth rates during development emphasize the importance of oscillatory patterns during lens epithelial cell proliferation, differentiation, and tissue development.

Animals↗
PubMed1992

Bilateral facial paralysis: a case presentation and literature review.

Bilateral facial paralysis is a diagnostic challenge, which may manifest itself as either a simultaneous or alternating form, occurring in 0.3-2.0% of patients that present with facial paralysis. The differential diagnosis of facial paralysis includes congenital, traumatic, neurologic, infectious, metabolic, neoplastic, toxic, iatrogenic and idiopathic etiologies. While idiopathic facial paralysis is the most common diagnosis, a comprehensive evaluation must be completed prior to this diagnosis in patients with bilateral facial paralysis. A representative case of simultaneous bilateral facial paralysis is presented. The literature is reviewed and discussed. A diagnostic protocol for the evaluation of bilateral facial paralysis is proposed. Bilateral facial paralysis requires a thorough evaluation and may prove to be a diagnostic dilemma.

Aged↗
PubMed1991

The 2.3 angstrom X-ray structure of nitrite reductase from Achromobacter cycloclastes.

The three-dimensional crystal structure of the copper-containing nitrite reductase (NIR) from Achromobacter cycloclastes has been determined to 2.3 angstrom (A) resolution by isomorphous replacement. The monomer has two Greek key beta-barrel domains similar to that of plastocyanin and contains two copper sites. The enzyme is a trimer both in the crystal and in solution. The two copper atoms in the monomer comprise one type I copper site (Cu-I; two His, one Cys, and one Met ligands) and one putative type II copper site (Cu-II; three His and one solvent ligands). Although ligated by adjacent amino acids Cu-I and Cu-II are approximately 12.5 A apart. Cu-II is bound with nearly perfect tetrahedral geometry by residues not within a single monomer, but from each of two monomers of the trimer. The Cu-II site is at the bottom of a 12 A deep solvent channel and is the site to which the substrate (NO2-) binds, as evidenced by difference density maps of substrate-soaked and native crystals.

Alcaligenes↗
PubMed1991

Magnetic resonance imaging of the facial nerve during Bell's palsy.

Twenty-five patients with Bell's palsy were evaluated to assess the efficacy of gadolinium (Gd+)-enhanced MRI in determining: (1) the site of facial nerve enhancement, (2) the relationship between EMG findings and Gd+ MRIs, and (3) the usefulness of Gd+ MRI in predicting recovery of facial function. Eighteen of twenty-five patients had enhancement of the facial nerve during Gd+ MRI whereas seven did not. The most common areas of facial nerve enhancement were the labyrinthine, geniculate ganglion, and proximal tympanic segments of the facial nerve. EMGs were performed on ten patients who lost nerve excitability. The segments of facial nerve enhanced during Gd+ MRI varied in location and intensity in patients who maintained nerve excitability and in patients who lost nerve excitability. There was no correlation between EMG findings and location of facial nerve enhancement in patients who lost nerve excitability. The location of facial nerve enhancement during Gd+ MRI was not useful in predicting recovery of facial paralysis.

Adolescent↗
PubMed1990

Human recombinant factor XIII from Saccharomyces cerevisiae. Crystallization and preliminary x-ray data.

Crystals of human recombinant factor XIII from the yeast Saccharomyces cerevisiae have been grown from solutions of ammonium sulfate at pH 5.8. The crystals are orthorhombic, with space group P2(1)2(1)2 and unit cell dimensions gamma a = 101.2, b = 182.7, and c = 93.4 A. The asymmetric unit consists of one a2 dimer of molecular mass 166 kDa. A 3.5-A resolution data set for the native protein has been collected. Practical resolution limits for these crystals have not been determined, but reflections have been observed to a Bragg spacing of 2.8-A resolution.

Crystallization↗
PubMed1990

Expression, purification, and characterization of human factor XIII in Saccharomyces cerevisiae.

Factor XIII is the terminal enzyme of the clotting cascade. A cDNA sequence encoding human placental factor XIII was expressed in Saccharomyces cerevisiae with the yeast ADH2-4c promoter. Expression levels were a strong function of the noncoding flanking DNA content of the construction. When the terminal 3'-flanking noncoding DNA was removed, expression increased approximately 50-fold. The protein was produced in quantity by high-yield fermentation and purified to homogeneity. The recombinant protein was cleaved by thrombin at the same activation site as purified human placental FXIII and exhibited 100% enzymatic activity. At high thrombin concentrations rFXIIIa was cleaved into inactive 54- and 25-kDa polypeptides. The identity of these cleavage sites and the blocked N-terminus to that of the human protein was revealed by amino acid microsequencing. A time course of thrombin activation was performed and the relative distribution of the thrombin-cleaved subunits to the uncleaved zymogen subunits determined; the results were consistent with the half of the sites catalytic model for transglutaminase activity proposed by Chung et al. (Chung, S. I., Lewis, M. S., & Folk, J. E. (1974) J. Biol. Chem. 249, 940-950, 1974) and Hornyak et al. (Hornyak, T. J., Bishop, P. D., & Shafer, J. A. (1989) Biochemistry 28, 7326-7332). Equilibrium and velocity sedimentation analysis indicated that rFXIII exists as a 166-kDa nondissociating dimer that behaves as a compact particle of 8.02 S. Thus, all of the properties of rFXIII thus far examined are consistent with those reported for human platelet and placental FXIII.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1989

The use of metrizamide for stabilizing against convection in sedimentation equilibrium.

In meniscus depletion sedimentation equilibrium experiments, the solute concentration gradient in much of the cell is insufficient to stabilize against thermal convection. Experiments with spectrin at 35 degrees C led to sufficient convection that, particularly at low concentrations of solute, no apparent redistribution occurred. At low angular velocity, the density gradient provided by moderate concentrations of NaCl or additional sucrose is inadequate to overcome the convective disturbances. We have found that the use of low concentrations of metrizamide can overcome these problems. The higher molecular weight and lower partial specific volume of metrizamide vis-a-vis sucrose allow a significant and stabilizing density gradient even at angular velocities below 8000 rpm.

Centrifugation, Density Gradient↗
PubMed1989

Oscillatory insulin secretion in perifused isolated rat islets.

After a step-function increase in glucose concentration, insulin secretion by perifused isolated rat islets of Langerhans showed oscillations superimposed on the well-known first- and second-phase secretory components. The oscillations were sustained for the length of the experiment and corresponded to at least four cycles. This established the existence of an oscillatory pacemaker with a narrow dispersion of periodicities intrinsic to the islets and showed that synchronization of islet action could be achieved by a step-function increase in glucose concentration. The observed period of 16 min is similar to the period of oscillatory insulin secretion in a number of intact organisms. This argues for identity of pacemakers in vivo and in isolated islets. This means that neural or other forms of interislet communication are not prerequisites for oscillatory insulin secretion. Theophylline increased the length of the oscillatory period, suggesting the periodicity of the pacemaker of insulin secretion can be metabolically regulated. This observation also provided a basis for explaining fine tuning of oscillatory periods by the nervous system.

Animals↗
PubMed1988

Sedimentation equilibrium analysis of five lipocortin-related phospholipase A2 inhibitors from human placenta. Evidence against a mechanistically relevant association between enzyme and inhibitor.

Five proteins from human placenta capable of inhibiting pancreatic phospholipase A2 were purified. Two of these proteins were identified as lipocortins I and II. The other three proteins were immunologically distinct from lipocortins I and II and had apparent subunit molecular masses of 32, 33, and 73 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Amino acid sequence analysis of peptides produced by cyanogen bromide digestion indicated sequence homology of these proteins with lipocortin I and the heavy chain subunit of lipocortin II. Two of these proteins were identified as endonexin II and 67-kDa calelectrin. The third protein appears to be the human form of bovine endonexin I, also characterized as porcine protein II. Sedimentation equilibrium analysis of lipocortin I, endonexin I and II, and the 67-kDa calelectrin suggested monomer-dimer equilibria with dissociation constants in the range of 0.33-1.3 X 10(-3) M and monomer molecular masses of 38,050, 36,400, 36,850, and 73,610 Da, respectively. Self-association of lipocortin II was described by dimerization of a protomer (K12 = 5.3 x 10(-7) M), followed by an indefinite self-association of the dimer (isodesmic dissociation constant, Kiso = 3.6 x 10(-6) M). The protomer molecular mass was 48,800 Da, consistent with a heterodimeric structure composed of one heavy (38,600 Da) and one light (10,944 Da) chain as previously characterized for lipocortin II. Sedimentation equilibrium analysis of mixtures of individual protein inhibitors and purified pancreatic phospholipase A2 indicated weak association between enzyme and inhibitor (Kd greater than or equal to 3 x 10(-5) M), insufficient to account for the observed inhibition of enzyme activity.

Annexin A5↗
PubMed1987

Purification and characterization of proteoliaisin, a coordinating protein in fertilization envelope assembly.

We report the purification and characterization of proteoliaisin, a protein that participates in the assembly of the sea urchin fertilization envelope. Proteoliaisin was purified from egg cortical granule exudate to greater than 99% homogeneity using chromatography on DEAE-Sepharose and on phenyl-Sepharose. Native proteoliaisin is a highly asymmetric protein (f/fo = 2.0) composed of a single Mr approximately 230,000 peptide. Its asymmetry was demonstrated both by analytical ultracentrifugation and by nondenaturing polyacrylamide gel electrophoresis, a novel analysis that detects molecular asymmetry in heterogeneous protein mixtures. Proteoliaisin is enriched in six amino acids: aspartic acid/asparagine, glutamic acid/glutamine, glycine, and cysteine, which account for over 50% of its mass. Nearly all of the cysteine residues are disulfide bonded. The protein contains a small proportion of aromatic amino acids with phenylalanine greater than tyrosine greater than tryptophan. At neutral pH its absorbance maximum is at 274.5 nm, with an extinction coefficient of 0.43 ml mg-1 cm-1. Proteoliaisin forms a 1:1 Ca2+-stabilized complex with ovoperoxidase, another component of the fertilization envelope, with Kd = 1.1 X 10(-6) M. Proteoliaisin, a constituent of the specialized echinoderm extracellular matrix called the fertilization envelope, has certain structural similarities to mammalian extracellular matrix proteins.

Amino Acids↗
PubMed1986

Self-association and active enzyme forms of Naja naja naja and Crotalus atrox phospholipase A2 studied by analytical ultracentrifugation.

The dimerization of phospholipase A2 (PLPA2) from Naja naja naja (Pakistani cobra) and Crotalus atrox (Western Diamondback rattlesnake) has been studied from pH 2.5 to 11 at 20 degrees C in 1 mM CaCl2, 0.21 M ionic strength. For the C. atrox enzyme, it was found necessary to use a combination of sedimentation equilibrium and fluorescence yield data to analyze the association. Sedimentation equilibrium in the analytical ultracentrifuge sufficed for the study of the N. naja PLPA2. In the region of enzymatic activity at pH 8, the dimerization association constants found were k2 = 2.8 X 10(6) L/mol and k2 = 6.9 X 10(4) L/mol for the C. atrox and N. naja enzymes, respectively. Analytical linked functions are presented which describe the data. Because the associations are linked to Ca2+ as well as the hydrogen ion, no attempt was made to interpret the ionization of residues in terms of the molecular structure. Active-enzyme sedimentation velocity experiments have been used to study the relation between enzymatic activity and association for both the C. atrox and N. naja enzymes. The substrate 1,2-dibutyryl-sn-glycero-3-phosphocholine (diC4PC) did not dissociate the C. atrox PLPA2. The substrate 1,2-dihexanoyl-sn-glycero-3-phosphocholine (diC6PC) at 7.5 mM dissociated the C. atrox PLPA2 when monitored either as the active enzyme or as the Sr2+-inhibited enzyme. At low enzyme concentrations, 40 mM diC4PC had no effect on N. naja PLPA2 dimerization. However, the sedimentation coefficients observed at enzyme concentrations above 0.2 mg/mL in active-enzyme sedimentation velocity experiments were larger than the values predicted from the thermodynamic studies. Sedimentation coefficients observed for the N. naja PLPA2 acting on diC6PC were larger than those of the monomeric protein, which was the form layered on this substrate. The dissociation of the C. atrox PLPA2 effected by diC6PC was analyzed by the thermodynamics of association and the kinetic Michaelis constant. The analysis suffices to account for the observed sedimentation coefficient. The sedimentation behavior of the N. naja PLPA2 acting on diC6PC substrate was analyzed in terms of a protein-lipid complex. With this model, 68 +/- 16 phospholipid molecules per protein monomer were determined. It is proposed that this enzyme has two micelle nucleation sites per monomer. These putative sites promote micelle formation of the substrate on the enzyme below the critical micelle concentration of the lipid alone.

Animals↗
PubMed1986

Equilibrium binding of insulin to rat white fat cells at 15 degrees C.

Equilibrium binding of insulin to isolated rat epididymal fat cells was investigated. A temperature of 15 degrees C was chosen for the study to minimize lysosomal degradation of insulin. Indeed, medium insulin lost only 1% of its precipitability in trichloroacetic acid during the 4-h incubation required to approach equilibrium. Binding was measured by a method that did not perturb the equilibrium of the system. A new formalism for analyzing binding data in general was introduced. A correction for trapping of insulin in the interstitial space of cell pellets was both necessary and sufficient to derive specific binding data from raw observations. Thus, so-called "nonspecific binding" was unmasked as a misnomer, and the expression "correction for trapping" was proposed as a substitute. Equations for one and two independent classes of binding sites were fit to the data by the method of maximum likelihood, and the best fit was selected based on Akaike's information criterion, as adapted for a constant fractional error. More than 99.7% of the binding sites were found to be describable by a simple binding isotherm with Kd,app = 8.8 multiplied by over divided by 1.3 nM. Less than 0.3% sites had a higher affinity (Kd approximately equal to 8 multiplied by over divided by 3 pM). There were 99,000 x/divided by 1.6 binding sites/cell. These equilibrium parameters are in agreement with values derived from a kinetic analysis, presented in the subsequent paper (Lipkin, E. W., Teller, D. C., and de Haën, C. (1986) J. Biol. Chem. 260, 1702-1711).

Adipose Tissue↗
PubMed1986

Kinetics of insulin binding to rat white fat cells at 15 degrees C.

The kinetics of insulin binding to isolated rat epididymal fat cells was investigated at 15 degrees C, at which temperature the system was simplified by the absence of lysosomal insulin degradation. The data were fit by maximum likelihood criteria with differential equations describing a number of models for the interaction of insulin and cells. Among those models that yielded a fit, the selection criteria were minimization of the Akaike information criterion and compatibility of the overall equilibrium constant for the system calculated from rate constants with the previously obtained experimental value. The results of the analysis indicated that insulin, I, first reversibly bound to cell surface receptors, R, whereupon this initial insulin-receptor complex, RI, reversibly altered its state or cellular location to R'I, according to the following equation. (Formula: see text) No evidence was found that insulin could either associate or dissociate from R'I directly. The association rate constant was kappa 12 = 1.6 x/divided by 1.4 X 10(5) liter mol-1 s-1, a value shown to be incompatible with diffusion control. The other rate constants were: kappa 21 = 3.4 x/divided by 1.6 X 10(-3) s-1, kappa 23 = 3.2 x/divided by 1.5 X 10(-4) s-1, and kappa 32 = 2.0 x/divided by 1.5 X 10(-4) s-1. From these rate constants, an equilibrium constant of 8.4 x/divided by 1.5 nM was calculated, in excellent agreement with the previously measured value of 8.8 x/divided by 1.3 nM (Lipkin, E. W., Teller, D. C., and de Haën, C. (1986) J. Biol. Chem. 260, 1694-1701). The kinetic analysis also yielded receptor numbers similar to those obtained by equilibrium binding studies. The nature of the R'I state is discussed in terms of an internalized state, in terms of insulin receptor complex in caveolae, in terms of receptor aggregates, and in terms of being a Michaelis complex between insulin bound to the receptor and cell surface-bound insulin protease.

Adipose Tissue↗