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Biomedical subjects

G Pfeifer

Publications and source records attributed to G Pfeifer.

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

The molecular chaperone TF55. Assessment of symmetry.

TF55-like factor from Sulfolobus solfataricus was purified to homogeneity and analyzed by electron microscopy and image analysis to determine the symmetries of these particles. Three different procedures were used to analyze the electron micrographs: (1) fuzzy-set based classification of the particles according to their rotational power spectra; (2) multivariate statistical analysis based on singular value decomposition; (3) circular harmonic analysis. Averages obtained from the three methods show unequivocally that the TF55-like complex presents a 9-fold symmetry.

Archaeal Proteins↗
PubMed1993

Two-dimensional crystals of the molecular chaperone GroEL reveal structural plasticity.

For two-dimensional (2-D) crystallization we have purified the molecular chaperone GroEL from Escherichia coli to homogeneity. The final and important step for crystallization in the purification procedure was an ATP-agarose column, on which the spacer between ATP and agarose was attached to C8 of adenine. Using the mica spreading "negative staining-carbon film" procedure and polyethylene glycol as a precipitant, we obtained four different 2-D periodic arrays. Two of them turned out to be true crystals. One crystal has P2 symmetry and lattice constants of a = 24.3 nm and b = 16.9 nm, the other has essentially P4 symmetry and shows smoothly varying local changes in the lattice parameters (a = b = 23 (+/- 1.3) nm). Very striking in the P4 crystal is the departure within each individual GroEL particle from the GroEL-typical seven-fold symmetry, which seems to be required for GroEL to accommodate to a crystal symmetry.

Bacterial Proteins↗
PubMed1992

Chaperonin-mediated protein folding: GroES binds to one end of the GroEL cylinder, which accommodates the protein substrate within its central cavity.

The mechanism of GroEL (chaperonin)-mediated protein folding is only partially understood. We have analysed structural and functional properties of the interaction between GroEL and the co-chaperonin GroES. The stoichiometry of the GroEL 14mer and the GroES 7mer in the functional holo-chaperonin is 1:1. GroES protects half of the GroEL subunits from proteolytic truncation of the approximately 50 C-terminal residues. Removal of this region results in an inhibition of the GroEL ATPase, mimicking the effect of GroES on full-length GroEL. Image analysis of electron micrographs revealed that GroES binding triggers conspicuous conformational changes both in the GroES adjacent end and at the opposite end of the GroEL cylinder. This apparently prohibits the association of a second GroES oligomer. Addition of denatured polypeptide leads to the appearance of irregularly shaped, stain-excluding masses within the GroEL double-ring, which are larger with bound alcohol oxidase (75 kDa) than with rhodanese (35 kDa). We conclude that the functional complex of GroEL and GroES is characterized by asymmetrical binding of GroES to one end of the GroEL cylinder and suggest that binding of the substrate protein occurs within the central cavity of GroEL.

Bacterial Proteins↗
PubMed1992

Complementary cultures in children's psychotherapy groups: conflict, coexistence, and convergence in group development.

This article presents a model for understanding development within children's psychotherapy groups. It is proposed that two complementary cultures exist within children's groups, one, indigenous peer culture, strictly of the children's making and the other, therapeutic group culture, created by the therapist in collaboration with group members. The therapist is wise to approach indigenous peer culture as an ethnographer might a native culture, with an emphasis on observation and seeking understanding rather than on intervention. The therapist can use the indigenous peer culture to speak to the children in their own language and eventually to engage them in collaboratively building a meaning system that is uniquely designed to address their psychotherapeutic needs. The article defines these concepts, develops them theoretically, and illustrates them clinically.

Adolescent↗
PubMed1991

The three-dimensional structure of proteasomes from Thermoplasma acidophilum as determined by electron microscopy using random conical tilting.

The three-dimensional structure of proteasomes from the archaebacterium Thermoplasma acidophilum has been determined to a resolution of approximately 2 nm from electron micrographs of negatively stained preparations using the method of 'random conical tilting'. The particles turn out to be essentially cylinder-shaped barrels, 15 nm long and 11 nm wide, enclosing a tripartite inner compartiment. An account is given of some of the present limitations which prevent to attain a higher resolution and possible ways to overcome these limitations are indicated.

Cysteine Endopeptidases↗
PubMed1991

The multicatalytic proteinase (prosome, proteasome): comparison of the eukaryotic and archaebacterial enzyme.

Proteasomes isolated and purified from rat muscle tissue and from the archaebacterium Thermoplasma acidophilum have a very similar size and shape, but the subunit composition is less complex in the archaebacterium as compared to the eukaryotic particle. The archaebacterial enzyme contains a catalytic site with chymotryptic specificity, which is inhibited by serine proteinase inhibitors and clearly differs from the eukaryotic particle which has a minimum of three catalytic sites for peptide bond hydrolysis of a yet undefined mechanism.

Amino Acid Sequence↗
PubMed1990

Electron microscopy and image analysis reveal common principles of organization in two large protein complexes: groEL-type proteins and proteasomes.

In an attempt to settle the question of whether the multicatalytic proteinase or proteasome exist in all three kingdoms of life--eukaryotes, archaebacteria, and eubacteria--we have undertaken a search for them in the eubacterium Comamonas acidovorans. We have, in fact, isolated and purified a cylinder-shaped particle. However, according to various structural and biochemical criteria this turned out to be more reminiscent of the groEL protein from Escherichia coli and its homologs than to proteasomes of eukaryotic or archaebacterial origin. N-terminal sequencing provided definite proof for its belonging to this family of molecular chaperonins. Image analysis of electron micrographs revealed that the C. acidovorans groEL-like protein and proteasomes in spite of their significantly different dimensions have certain principles of organization in common.

Amino Acid Sequence↗
PubMed1989

The multicatalytic proteinase (prosome) is ubiquitous from eukaryotes to archaebacteria.

From the thermoacidophilic archaebacterium, Thermoplasma acidophilum, a proteolytically active particle has been isolated which is almost identical in size and shape with the multicatalytic proteinase (prosome) from rat. This result indicates that prosomes have been developed early in evolution and that they possibly serve functions common to all living cells.

Animals↗
PubMed1988

Electron microscopy and image analysis of the multicatalytic proteinase.

One electron micrographs, negatively stained multicatalytic proteinase molecules are viewed end-on (ring shaped) or side-on (rectangular shaped). For aurothioglucose, ammonium molybdate- and phosphotungstate-stained molecules, the dimensions measured are consistent. In contrast, uranyl acetate-staining reveals ring-shaped particles which vary in diameter between 12 and 16 nm. This is due to a partial collapse and substantial flattening of the structure. Digital image analysis of side-on views of the particles reveals a tripartite, reel-shaped structure. Within the ring-like, end-on projections of ammonium molybdate-stained molecules six local centres of mass can be discerned; their position appears to depart, however, from a true six-fold symmetry.

Animals↗
PubMed1988

[Pathogen spectrum in suppurative meningitis with special reference to a patient sample].

In a five years period (1982 till 1986) the spectrum of pathogenic bacteria and fungi in acute meningitis was analysed. The appearance, spreading and suspected spectrum of pathogens have to be followed by special aspects considering effective therapeutic proceedings. 361 out of 392 positive cerebrospinal fluids (92.1%) were derived from only 3 (neurosurgical, neurological and pediatric department) out of 14 possible departments. Whereas in the pediatric department the classical pathogens of acute meningitis predominated, the patients in the neurosurgical department mainly showed nosocomial infections. There has to be considered the accidental infection, especially in the severely ill patients of the neurosurgical intensive care unit, which favours highly resistant pathogens. Furthermore, to initiate an infection, the pathogenicity of nosocomial microorganisms is not required to be high. The correlation of clinical signs and the proof of pathogens showed that often so called contaminants could be of higher value to be the infectious agent as assumed. Nevertheless, there seemed to be a regression of acute meningitis due to better diagnostic and therapeutic proceedings.

Adolescent↗