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Biomedical subjects

E Hartmann

Publications and source records attributed to E Hartmann.

At least 19 recordsLinked to original sources
PubMed1992

A mammalian homolog of SEC61p and SECYp is associated with ribosomes and nascent polypeptides during translocation.

SEC61p is essential for protein translocation across the endoplasmic reticulum membrane of S. cerevisiae. We have found a mammalian homolog that shows more than 50% sequence identity with the yeast protein. Moreover, several regions of SEC61p have significant similarities with corresponding ones of SecYp of bacteria, indicating a strong evolutionary conservation of the mechanism of protein translocation. Mammalian Sec61p, like the yeast protein, is located in the immediate vicinity of nascent polypeptides during their membrane passage. It is tightly associated with membrane-bound ribosomes, suggesting that the nascent chain passes directly from the ribosome into a protein-conducting channel. These results define Sec61p as a ubiquitous key component of the protein translocation apparatus.

Amino Acid Sequence↗
PubMed1992

A protein of the endoplasmic reticulum involved early in polypeptide translocation.

To identify components of the mammalian endoplasmic reticulum involved in the translocation of secretory proteins, crosslinking and reconstitution methods were combined. A multispanning abundant membrane glycoprotein was found which is in proximity to nascent chains early in translocation. In reconstituted proteoliposomes, this protein is stimulatory or required for the translocation of secretory proteins.

Amino Acid Sequence↗
PubMed1992

[Diagnosis of dysarthria with the "Munich Intelligibility Profile"--construction of the procedure and its use].

No German-based methods for reliable assessment of the intelligibility of dysarthric speech have yet been described. The techniques usually applied in clinical diagnostics take no account of the various factors influencing the understanding of spoken language. They also fail to differentiate between individual patterns of impaired intelligibility. The intelligibility profile presented here controls for the most relevant influencing factors and allows us to discern therapeutically relevant patterns of disturbed intelligibility. The principles of its construction and some applications are presented.

Cerebellar Diseases↗
PubMed1991

Effects of day care and maternal teaching on child educability.

Two groups of matched mother-child pairs, a day care sample (N = 38) and a home reared sample (N = 38) participated in a study testing mothers for degree of decentred teaching and children for degree of decentred educability. The children were seven years old. Mother and child were tested in separate settings, thus preventing interdependency among scores. The study used a matched-pair design with control of five background variables; age of the child, mother's educational level, mother's occupational status, family SES level, and type of family. The results showed strong positive effects of both day care experience and maternal teaching on child educability. Day care experience improved the educability of children independent of the mother's teaching strategy and gender of the child.

Achievement↗
PubMed1991

Nucleotide-activated oligosaccharides are intermediates of the cell wall polysaccharide of Methanosarcina barkeri.

The cell wall of Methanosarcina barkeri consists of a heteropolysaccharide (methanochondroitin), which resembles the eukaryotic chondroitin. From cell extracts of Methanosarcina barkeri four uridine diphosphate and one undecaprenyl pyrophosphate-activated intermediate(s) of the methanochondroitin were isolated. In contrast to the known biosynthetic pathways of polysaccharides from other prokaryotes and eukaryotes, nucleotide activated oligosaccharide precursors are involved in the case of the methanochondroitin. Usually, oligosaccharides are synthesized at the lipid stage.

Amino Sugars↗
PubMed1990

Isolation of nucleotide activated amino acid and peptide precursors of the pseudomurein of Methanobacterium thermoautotrophicum.

The following putative precursors of the pseudomurein were isolated from trichloroacetic acid extracts of Methanobacterium thermoautotrophicum: a uridine diphosphate activated derivative of glutamic acid and the uridine diphosphate activated peptides (see text). The activated glutamic acid residue and the three activated pepetides lack the glycan components N-acetylglucosamine and N-acetyltalosaminuronic acid present in the intact pseudomurein. In this case uridine diphosphate should be directly linked to the amino group of a glutamic acid residue, which represents a new mode of amino acid and peptide activation.

Amino Acid Sequence↗
PubMed1990

Structure and biosynthesis of the signal-sequence receptor.

The signal-sequence receptor (SSR) has previously been shown to be a component of the environment which nascent polypeptides meet on passage through the endoplasmic reticulum (ER) membrane. We report here on the primary structure of the SSR as deduced from cDNA clones and from direct protein sequencing. The glycoprotein is synthesized with a cleavable amino-terminal signal sequence and contains only one classical membrane-spanning segment. Its insertion into the ER membrane during biosynthesis depends on the function of the signal-recognition particle. SSR shows a remarkable charge distribution with the amino terminus being highly negatively charged, and the cytoplasmic carboxyl terminus positively charged. The SSR can be phosphorylated in its cytoplasmic tail both in intact cells and in a cell-free system, suggesting a regulation of its function. The localization of the protein in the ER membrane was confirmed by immunofluorescence microscopy.

Amino Acid Sequence↗
PubMed1990

Isolation of lipid activated pseudomurein precursors from Methanobacterium thermoautotrophicum.

From cell extracts of the pseudomurein possessing methanogen Methanobacterium thermoautotrophicum two putative pseudomurein precursors were isolated and characterized: (1) an undecaprenyl pyrophosphate activated disaccharide pentapeptide composed of N-acetylglucosamine, N-acetyltalosaminuronic acid, alanine, glutamic acid and lysine in a molar ratio of 1:1:2:2:1 and (2) the corresponding undecaprenyl pyrophosphate activated tetrapeptide lacking one alanine residue. The isolation of these precursors show that the biosynthesis of the eubacterial murein and the methanobacterial pseudomurein differs not only in the cytoplasmic step, as recently described, but also in the lipid stage.

Amino Acid Sequence↗
PubMed1990

Comparison of the biosynthesis of the methanobacterial pseudomurein and the eubacterial murein.

From cell extracts of the archaebacterium Methanobacterium thermoautotrophicum 11 putative precursors of the pseudomurein were isolated and characterized. On the basis of the isolated intermediates, a biosynthetic pathway of the pseudomurein is proposed. Compared to the eubacterial murein the biosynthetic stages follow different pathways as indicated by the occurrence of a nucleotide-activated disaccharide and nucleotide-activated peptides.

Amino Acid Sequence↗
PubMed1990

A novel pathway for secretory proteins?

In eukaryotes, most proteins which are transported to the extracellular space, into mitochondria or into chloroplasts are synthesized as precursor polypeptides containing cleavable N-terminal signal or targeting sequences. We have searched the literature for proteins that are exported from the cytosol without being proteolytically processed. Some of these proteins contain uncleaved signal or targeting sequences. However, among secretory proteins there is a class that does not possess hydrophobic signal sequences and appears to leave the cell by a secretory pathway clearly distinct from the classical route through the endoplasmic reticulum and Golgi apparatus.

Acylation↗
PubMed1990

The signal sequence receptor has a second subunit and is part of a translocation complex in the endoplasmic reticulum as probed by bifunctional reagents.

Bifunctional cross-linking reagents were used to probe the protein environment in the ER membrane of the signal sequence receptor (SSR), a 24-kD integral membrane glycoprotein (Wiedmann, M., T. V. Kurzchalia, E. Hartmann, and T. A. Rapoport. 1987. Nature [Lond.]. 328:830-833). The proximity of several polypeptides was demonstrated. A 22-kD glycoprotein was identified tightly bound to the 34-kD SSR even after membrane solubilization. The 34-kD polypeptide, now termed alpha SSR, and the 22-kD polypeptide, the beta SSR, represent a heterodimer. We report on the sequence of the beta SSR, its membrane topology, and on the mechanism of its integration into the membrane. Cross-linking also produced dimers of the alpha-subunit of the SSR indicating that oligomers of the SSR exist in the ER membrane. Various bifunctional cross-linking reagents were used to study the relation to ER membrane proteins of nascent chains of preprolactin and beta-lactamase at different stages of their translocation through the membrane. The predominant cross-linked products obtained in high yields contained the alpha SSR, indicating in conjunction with previous results that it is a major membrane protein in the neighborhood of translocating nascent chains of secretory proteins. The results support the existence of a translocon, a translocation complex involving the SSR, which constitutes the specific site of protein translocation across the ER membrane.

Amino Acid Sequence↗
PubMed1990

Segregation of the signal sequence receptor protein in the rough endoplasmic reticulum membrane.

The signal sequence receptor (SSR), an integral membrane glycoprotein of 34 kDa, has previously been shown to be a component of the molecular environment which nascent polypeptide chains meet in passage through the endoplasmic reticulum (ER) membrane. We have used antibodies directed against the SSR and both immunocytochemistry and cell fractionation to determine its distribution in rat liver cells. SSR was found largely restricted to the rough ER. Only small amounts of the protein were detected in smooth ER. These results provide further evidence for a functional differentiation of rough and smooth ER and for a role of SSR in protein translocation across the ER membrane.

Animals↗
PubMed1990

[Effect of removal of calculus on periodontium by hand- and roto-pro-instruments].

It was the aim of this clinically longitudinal study to find out the consequence of the removal of calculus with hand- and roto-pro-instruments of the periodontium in 50 patients suffering from periodontal diseases. There are no clinically provable differences between the two methods of the removal of calculus. Both methods cause a statistically significant effect on the inflammatory factors of the periodontium.

Dental Calculus↗
PubMed1989

Photocrosslinking demonstrates proximity of a 34 kDa membrane protein to different portions of preprolactin during translocation through the endoplasmic reticulum.

Photocrosslinking has been used to identify integral proteins of the endoplasmic reticulum membrane that are in proximity to nascent preprolactin during in vitro translocation. A photoreactive lysyl derivative was introduced into truncated preprolactin chains comprising 86 or 115 amino acids. Both with the 86mer, containing the reactive group in the signal sequence, and with the 115mer, containing the probe exclusively in the mature portion of the chain, photocrosslinking occurred to an approximately 35 kDa transmembrane glycoprotein, the signal sequence receptor (SSR). SSR is identical with a previously isolated abundant and ubiquitous 34 kDa membrane protein that appears to be essential for protein translocation.

Animals↗
PubMed1989

A membrane component of the endoplasmic reticulum that may be essential for protein translocation.

We have purified a glycosylated, membrane-spanning protein of relative molecular mass approximately 34,000 (Mr approximately 34 K) from canine microsomes that appears to be essential for protein translocation across the endoplasmic reticulum (ER) as shown by the inhibitory action of antibodies directed against it and of monovalent Fab-fragments produced from them. The ER membrane contains at least as many molecules of the 34 K membrane protein as bound ribosomes. The protein can be detected immunologically in tissues of various organisms, indicating an universal function.

Animals↗