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F Ackermann

Publications and source records attributed to F Ackermann.

12 recordsLinked to original sources
PubMed1999

Acromegaly in a family without a mutation in the menin gene.

Familial pituitary tumors are rare. Only 45 cases in 20 families with acromegaly have been reported. A third of the cases (30%) is related to multiple endocrine neoplasia type 1 (MEN 1). We report two cases of acromegaly in one family with pituitary macroadenomas. A 46-year-old woman with elevated serum growth hormone (GH) and insulin-like growth factor (IGF-1) and a failure to supress GH in the glucose tolerance test underwent transsphenoidal surgery 4 years ago. Three years later her 24-year-old son also presented with typical signs of acromegaly. A pituitary macroadenoma was identified by MRT and he also underwent transsphenoidal surgery. There were no symptoms of McCune-Albright syndrome or other forms of endocrine hyperfunction in the two patients. In an attempt to identify the molecular etiology of the tumours DNA was extracted from paraffin fixed tissue from both patients. Exon 7 to 13 of the Gsp-protein and exons 1 to 10 of the menin gene were amplified by PCR. Although Gsp mutations have been identified in 40% of somatotroph tumors, direct sequencing of the PCR products showed no mutations in exons 7 to 13 of Gs alpha. Moreover no mutations were found in exons 1 to 10 of the menin gene. Therefore, molecular causes other than Gsp or menin gene mutations have to be considered as the molecular etiology of acromegaly in this family.

Acromegaly↗
PubMed1999

Linkage of familial euthyroid goiter to the multinodular goiter-1 locus and exclusion of the candidate genes thyroglobulin, thyroperoxidase, and Na+/I- symporter.

Iodine deficiency is the most important etiological factor for euthyroid endemic goiter. However, family and twin pair studies also indicate a genetic predisposition for euthyroid simple goiter. In hypothyroid goiters several molecular defects in the thyroglobulin (TG), thyroperoxidase (TPO), and Na+/I- symporter (NIS) genes have been identified. The TSH receptor with its central role for thyroid function and growth is also a strong candidate gene. Therefore, we investigated a proposita with a relapsing euthyroid goiter and her family, in which several members underwent thyroidectomy for euthyroid goiter. Sequence analysis of the complementary DNA (cDNA) of the TPO and TSH receptor genes revealed several previously reported polymorphisms. As it is not possible to exclude a functional relevance for all polymorphisms, we opted for linkage analysis with microsatellite markers to investigate whether the candidate genes are involved in the pathogenesis of euthyroid goiter. The markers for the genes TG, TPO, and NIS gave two-point and multipoint logarithm of odds score analysis scores that were negative or below 1 for all assumed recombination fractions. As no significant evidence of linkage was found, we conclude that these candidate genes can be excluded as a major cause of the euthyroid goiters in this family. In contrast, we have found evidence for linkage of familial euthyroid goiter to the recently identified locus for familial multinodular nontoxic goiter (MNG-1) on chromosome 14q. The haplotype cosegregates clearly with familial euthyroid goiter. Our results provide the first confirmation for MNG-1 as a locus for nontoxic goiter.

Adolescent↗
PubMed1998

Mapping of linear antigenic determinants on glycoprotein C of herpes simplex virus type 1 and type 2 recognized by human serum immunoglobulin G antibodies.

Using membrane-based dekapeptides, the reactivity of human serum antibodies with linear antigenic determinants of herpes simplex virus (HSV) type 1 and type 2 glycoprotein C (gC-1, gC-2) was studied by pep scan and immunodot assay. The entire coding sequences of gC-1 and gC-2 were screened for the presence of linear epitopes by pep scan. Peptides recognized in an HSV-1 type-specific manner were mainly identified within the N-terminal third and at the C-terminus of gC-1, whereas most type-common antibodies were directed against colinear peptides within the central parts of gC-1 and gC-2. The type-specific reaction of human sera with gC-2 peptides in pep scan was poor. Eight peptides identified as immunoreactive by pep scan were further tested in immunodot assay for their reactivity with a human serum panel. None of the eight HSV-negative sera gave positive results by immunodot assay. Positive reactions with gC peptides were found to be strongly age-dependent, i.e., the rate of positive reactions was significantly higher in HSV-positive adults than in HSV-positive children. Antibody reactivity with two type-common gC peptides was demonstrated in 17 out of 28 HSV-positive sera. A putative type-specific gC-2 peptide employed in immunodot assay was inconsistently recognized by human sera. Twenty HSV-positive sera reacted with at least 1 of 5 type-specific gC-1 peptides. Nine sera showing no reactivity with glycoprotein G of HSV-1 (gG-1) by immunobloting recognized type-specific gC-1 peptides in immunodot assay. Thus, gC-1 peptides might allow the detection of HSV-1-specific antibodies in individuals showing no reactivity with commonly employed HSV-1-specific diagnostic antigenes, i.e., purified or recombinant gG-1.

Adult↗
PubMed1998

Estimation and filtering of potential protein-protein docking positions.

MOTIVATION: Software systems predicting automatically whether and how two proteins may interact are highly desirable, both for understanding biological processes and for the rational design of new proteins. As a part of a future complete solution to this problem, a bundle of programs is presented designed (i) to estimate initial docking positions for a given pair of docking candidates, (ii) to adjust them, and (iii) to filter them, thus preparing more detailed computations of free energies. RESULTS: The system is evaluated on a test set of 51 co-crystallized complexes aiming at redocking the subunits. It works completely automatically and the evaluation is performed using one single set of parameters for all complexes in the test set. The number of solutions is fixed to 50 positions with a median CPU time of 26 min. For 30 complexes, these contain a near-correct solution with root mean square deviation ( RMSD ) </=5.0 A, which is ranked first in five cases. For all complexes, the best solution is scored on rank 16 as the worst case, and has a median RMSD of 4.3 A. Alternatively to this initial estimation of docking positions, a global sampling of rotations was tested. Whereas this yields top-ranked solutions with RMSD </=3.0 A for all 51 complexes, the median CPU time increases to 11 h. This shows that this blind sampling is not feasible for most applications. AVAILABILITY: The system and its components are available on request from the authors. CONTACT: friedric@techfak.uni-bielefeld or posch@techfak.uni-bielefeld.de

Algorithms↗
PubMed1996

viwish: a visualization server for protein modelling and docking.

A visualization tool viwish for proteins based on the Tcl command language has been developed. The system is completely menu driven and can display arbitrary many proteins in arbitrary many windows. It isinstantly t o use, even for non computer experts and provides possibilities to modify menus, configurations, and windows. It may be used as a stand-alone molecular graphics package or as a graphics server for external programs. Communications with these client applications is established even across different machines (through the send command to Tk, an extension of Tcl). In addition, a wide rage of chemical data like molecular surfaces and 3D gridded samplings of chemical features can be displayed. Therefore the systmen is especially useful for the development of algorithms that need visual distributed freely, including the source code.

Binding Sites↗
PubMed1995

Spectroscopic, calorimetric, and kinetic demonstration of conformational adaptation in peptide-antibody recognition.

Little is known about the extent to which protein flexibility contributes to antigen-antibody recognition and cross-reactivity. Using short coil peptides (leucine zippers) as model antigens, we demonstrate that a monoclonal antibody can force a noncognate peptide into a conformation that is similar to the conformation of the cognate peptide against which the monoclonal antibody is directed. Monoclonal antibodies 29AB and 13AD were raised against the 29-residue peptide LZ (Ac-EYEALEKKLAALEAKLQALEKKLEALEHG-amide) that forms a very stable coiled coil. The two antibodies cross-reacted strongly with the random coil analogue LZ(7P14P) that contains Lys-->Pro and Ala-->Pro substitutions in positions 7 and 14, respectively. The antibody-bound peptide LZ(7P14P) adopted an altered conformation that possibly was coiled coil-like, as shown by CD difference spectroscopy and fluorescence quenching experiments on coumarin-labeled peptides. Isothermal titration calorimetry revealed that the cross-reaction of antibodies 13AD and 29AB with the random coil peptide LZ(7P14P) exhibited a large unfavorable entropy. This, however, was strongly compensated by a more favorable enthalpy, resulting in only a small difference between the association constants for peptide LZ and LZ(7P14P), respectively. To investigate the opposite type of cross-reaction, monoclonal antibody 42PF was raised against the random coil peptide LZ(7P14P). 42PF cross-reacted with coiled coil peptide LZ by forcing it to dissociate into single chains. Enthalpy/entropy compensation again enabled the cross-reaction, which now was entropically favored and enthalpically disfavored. The rate of reaction of antibody 42PF with peptide LZ was controlled by the rate of dissociation of LZ into single chains. This observation, as well as the generally much slower reaction rate with the noncognate peptides, indicated that the cross-reactivity occurred because the antibody selected the conformer of the antigen that binds the strongest, a mechanism we call "induced fit by conformational selection."

Amino Acid Sequence↗
PubMed1995

Protein docking combining symbolic descriptions of molecular surfaces and grid-based scoring functions.

With the growing number of known 3D protein structures, computing systems, that can predict where two protein molecules interact with each other is becoming of increasing interest. A system is presented, integrating preprocessing like the computation of molecular surfaces, segmentation, and searching for complementarity in the general framework of a pattern analyzing semantic network (ERNEST). The score of coarse symbolic computations is used by the problem independent control strategy of ERNEST to guide a more detailed analysis considering steric clash and judgements based on grid-based surface representations. Successful examples of the docking system are discussed that compare well with other approaches.

Binding Sites↗
PubMed1994

Genuine and apparent cross-reaction of polyclonal antibodies to proteins and peptides.

Antiserum to a native protein may cross-react with the corresponding denatured protein or with peptides. The cross-reaction is either a genuine property of the antibodies or caused by antibodies produced against some unfolded protein contaminating the native protein used for immunization. Appropriate conformation-sensitive immunoassays must be employed to distinguish a genuine from an apparent cross-reaction. In the present study, we have analyzed critically the cross-reaction of rabbit antisera against proteins and peptides. We have distinguished between genuine and apparent cross-reaction with the help of the protein A antibody-capture ELISA, a new conformation-sensitive ELISA format. Three systems were analyzed: cross-reaction of antisera to native yeast and horse cytochrome c with unfolded apo-cytochrome c; cross-reaction of antisera to a coiled-coil leucine-zipper peptide with a homologous random-coil peptide obtained by introducing two proline residues into the leucine-zipper sequence; cross-reaction of antisera to two peptides that correspond to the N-terminal and an internal sequence of ferredoxin: NADP+ reductase (FNR), with the native enzyme. The reaction of the anti-(cytochrome c) sera was clearly due to antibodies produced against unfolded protein, it was an apparent and not a genuine cross-reaction. Furthermore, the apparently cross-reactive antibodies to horse cytochrome c did not discriminate against sequence-related proteins from dog, beef, rabbit and pigeon. In contrast, antibodies to the leucine-zipper peptide did cross-react in a genuine way with the homologous random-coil peptide, that is, the cross-reactive antibodies do not seem to have been produced against the unfolded form of the leucine-zipper peptide. Of the two anti-peptide sera the one against the unstructured and highly accessible N-terminal segment reacted strongly with the native protein. The second serum against a solvent-accessible turn-like sequence of FNR showed apparent cross-reactivity: antibodies recognizing the native protein were directed against a minor conformational isoform of the free peptide and did not react with the principal form(s) of the free peptide. The generation of cross-reactive antibodies depends on the conformational stability and integrity of the immunogen and on the molecular form of its application, i.e., free, polymerized or carrier-bound. The results clarify the different nature of cross-reactivity of antisera to proteins and peptides. This knowledge is crucial if antisera are to be used as conformation-specific probes.

Amino Acid Sequence↗
PubMed1993

Protein A antibody-capture ELISA (PACE): an ELISA format to avoid denaturation of surface-adsorbed antigens.

Adsorption to a polymeric surface may severely alter the antigenic structure of proteins through unfolding. A conventional capture ELISA in which a protein antigen is adsorbed to the microtiter plate may be unsuitable for testing the specificity of antibodies directed against native proteins (C. Schwab and H.R. Bosshard (1992) J. Immunol. Methods 147, 125). This problem can be overcome by PACE, a new ELISA procedure in which monoclonal or polyclonal antibodies are first allowed to equilibrate with biotinylated antigen in solution. Thereafter, the antigen-antibody complex (and free antibody) is bound to the microtiter plate through protein A. Captured antigen-antibody complex is detected by streptavidin-alkaline phosphatase and p-nitrophenylphosphate. A competition assay is accomplished by co-incubation of biotinylated and non-biotinylated antigens before capture to the protein A-coated plate. PACE combines the advantages of a solution-phase immunoassay (Farr assay) with the ease of a solid-phase ELISA. PACE has been used to test the conformational specificity of polyclonal and monoclonal antibodies against native and denatured cytochrome c, and of a polyclonal antiserum against a coiled coil leucine zipper peptide. Since a biotin group can be attached specifically to the N-terminal residue of synthetic peptides, PACE is also useful for assaying reactivity against peptide antigens which are difficult to adsorb to microtiter plates.

Amino Acid Sequence↗
PubMed1993

Binding of ferredoxin to ferredoxin:NADP+ oxidoreductase: the role of carboxyl groups, electrostatic surface potential, and molecular dipole moment.

The small, soluble, (2Fe-2S)-containing protein ferredoxin (Fd) mediates electron transfer from the chloroplast photosystem I to ferredoxin: NADP+ oxidoreductase (FNR), a flavoenzyme located on the stromal side of the thylakoid membrane. Ferredoxin and FNR form a 1:1 complex, which is stabilized by electrostatic interactions between acidic residues of Fd and basic residues of FNR. We have used differential chemical modification of Fd to locate aspartic and glutamic acid residues at the intermolecular interface of the Fd:FNR complex (both proteins from spinach). Carboxyl groups of free and FNR-bound Fd were amidated with carbodiimide/2-aminoethane sulfonic acid (taurine). The differential reactivity of carboxyl groups was assessed by double isotope labeling. Residues protected in the Fd:FNR complex were D-26, E-29, E-30, D-34, D-65, and D-66. The protected residues belong to two domains of negative electrostatic surface potential on either side of the iron-sulfur cluster. The negative end of the molecular dipole moment vector of Fd (377 Debye) is close to the iron-sulfur cluster, in the center of the area demarcated by the protected carboxyl groups. The molecular dipole moment and the asymmetric surface potential may help to orient Fd in the reaction with FNR. In support, we find complementary domains of positive electrostatic potential on either side of the FAD redox center of FNR. The results allow a binding model for the Fd:FNR complex to be constructed.

Amino Acid Sequence↗
PubMed1978

[Sex hormone binding globulin (SHBG), a new metabolic in vitro thyroid function test].

SHBG (sex hormone binding globulin) is a carrier protein for the sex hormones testosterone and estradiol with a molecular weight of about 95000 dalton. It can be used as a metabolic test of thyroid function. SHBG was measured by the adsorption method of Mickelson and Petra; the SHBG contained in serum is incubated with 3H-5alpha-dihydrotestosterone and adsorbed to a cellulose filter. Thirty-eight female patients with hyperthyroidism before treatment had markedly elevated levels of SHBG (x +/- SD: 4.85 +/- 2.4 microgram DHT/100 ml) compared with normal controls (1.50 +/- 0.57; p is less than 0.001). A good correlation between the thyroid hormones and SHBG could be domonstrated which was better for T3 than for T4:r =0.76 (p is less than 0.001) for T3 and r= 0.65 (p is less than 0.001) for T4. This agrees with the clinical finding that the circulating T3 level is a better index of the metabolic severity of thyrotoxicosis than T4. After radioiodine treatment SHBG returns to normal values in euthyroid patients (1.38 +/- 0.8; n = 15) and remains elevated in persistent hyperthyroidism (3.99 +/-1,6; n = 67). Even in patients with persistent biochemical hyperthyroidism who are completely euthyroid on clinical examination, SHBG remains high. Despite lack of evidence of clinical hyperthyroidism, this metabolic test demonstrates the biologic significance of merely biochemical hyperthyroidism. Estimation of SHBG as a metabolic thyroid function test in vitro is of special value for the evaluation of patients showing discrepancies between the clinical and biochemical states and for borderline hyperthyroidism.

Carrier Proteins↗