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Biomedical subjects

U Henning

Publications and source records attributed to U Henning.

At least 91 records · Page 5Linked to original sources
PubMed1981

Precursor proteins are intermediates in vivo in the synthesis of two major outer membrane proteins, the OmpA and OmpF proteins, of Escherichia coli K12.

The OmpA and OmpF proteins are major outer membrane proteins of Escherichia coli K12. Their precursors, the pro-OmpA and pro-OmpF proteins, have been detected in vivo in pulse-labelling experiments carried out with [35S]methionine at 25 degrees C. Wehn the pulse was at 37 degrees C, however, no precursors were detected. The pulse-labelled precursors were processed rapidly and quantitatively into mature protein at 25 degrees C. The apparent half-life of the pro-OmpF protein was estimated to be 30 s, and the pro-OmpA protein may be processed even faster. In short pulses (10 s) the precursors of both proteins were the predominant labelled species, indicating that at 25 degrees C processing does not start until chain elongation of the precursor is almost, if not entirely, complete. When French press lysates of cells pulse-labelled for 10 s were subjected to sucrose gradient centrifugation to separate the inner and outer membranes, both precursors comigrated with the inner membrane.

Centrifugation, Density Gradient↗
PubMed1980

Primary structure of major outer membrane protein II (ompA protein) of Escherichia coli K-12.

The amino acid sequence of major outer membrane protein II (ompA protein) from Escherichia coli K-12 has been determined. The transmembrane polypeptide consists of 325 residues, resulting in a molecular weight of 35,159. The transmembrane part of the protein is located between residues 1 and 177. In this part of the protein a predominantly lipophilic 27-residue segment exists that perhaps spans the membrane in a mostly alpha-helical conformation, or a 19-residue stretch of this segment might traverse the membrane linearly. Inside the outer membrane a sequence -Ala-Pro-Ala-Pro-Ala-Pro-Ala-Pro- exists that, analogous to the -Cys-Pro-Pro-Cys-Pro- sequence in the hinge region of immunoglobulin, could assume the conformation of a polyproline helix. Computer analysis did not reveal a clear overall pattern of internal homology in the protein; besides the -Ala-Pro- repeat, only one local area (two adjacent dodecapeptide segments) shows some repetitiveness. The same analysis did not produce evidence for internal homology in the previously determined sequence of outer membrane protein I (porin) nor was any marked resemblance detected between transmembrane proteins I and II.

Amino Acid Sequence↗
PubMed1979

Primary structure of major outer membrane protein I of Escherichia coli B/r.

The amino acid sequence of the pore-forming outer membrane protein I (porin) from Escherichia coli B/r has been determined. The polypeptide contains 340 amino acid residues resulting in a molecular weight of 37,205. The transmembrane polypeptide has no stretches of nonpolar residues, uninterrupted by charged side chains, longer than 11 amino acid residues. Regarding polarity, the chain can be subdivided into three regions: a distinctly hydrophilic region between residues 1 and 82 (51.2% polarity), a fairly nonpolar region between residues 83 and 194 (33.9% polarity), and a more hydrophilic region up to the COOH terminus (48% polarity). These results are interpreted as evidence against a simple transmembrane structure in which the membrane is spanned by a single contiguous sequence of hydrophobic amino acids, as has been proposed, for example, for glycophorin.

Amino Acid Sequence↗
PubMed1979

Cloning of the structural gene (ompA) for an integral outer membrane protein of Escherichia coli K-12.

The gene (ompA) for the major outer membrane protein II* from Escherichia coli K-12 has been cloned on a 5-megadalton EcoRI fragment by using phage lambda as vector. The gene is expressed during the lytic cycle of the recombinant phage and the insoluble membrane-bound protein was detected in phage plaques with a simple radioimmunoassay. Transfer of the EcoRI fragment into plasmid pSC101 and expression in a host lacking protein II* led to overproduction of protein II* and decreased production of two other major outer membrane proteins. Expression of the plasmid pSC101-ompA+ in minicells derived from an ompA minicell-producing strain led to synthesis, at high rates, of this protein and massive accumulation of a second cell envelope protein most likely representing the biosynthetic precursor of protein II*.

Bacterial Proteins↗
PubMed1979

Protein I and protein II from the outer membrane of Escherichia coli are mouse B-lymphocyte mitogens.

Protein I from the outer membrane of Escherichia coli is a B-lymphocyte mitogen in mice. Polyclonal activation of mouse splenocytes was demonstrated by 3H-thymidine incorporation into DNA, 3H-uridine incorporation into RNA, and by a hemolytic plaque assay in three inbred mouse strains. B-lymphocytes from LPS responder mice (C57Bl/10, STU/nu/nu) and LPS non-responder mice (C3H/HeJ) both responded well to protein I. The presence of serum was not necessary for mitogenicity; bovine serum albumin exhibited a beneficial effect on serum-depleted cultures. Thymocytes of C3H/HeJ mice were not activated by protein I. Protein II* from E. coli was also tested in our systems and showed a weak B-lymphocyte stimulatory activity. Human peripheral blood lymphocytes were not activated.

Animals↗
PubMed1978

Major proteins of the outer cell envelope membrane of Escherichia coli K12: multiple species of protein I differ in primary structure.

Protein I, one of the major outer membrane proteins of E. coli in most K12 strains is represented by two very similar polypeptides Ia and Ib. Sequential mutations (involving selections for phage resistance) can lead to loss of proteins Ia and Ib. Among "revertants" of such Ia-Ib- mutants clones exist that instead of Ia or Ib produce a third species of protein I, polypeptide Ic. Ichihara and Mizushima [J. Biochem. 83, 1095--1100 (1978)] have shown that proteins Ia and Ib exhibit differences in primary structure. Here evidence is presented indicating that protein Ic also is not identical in primary structure with Ia or Ib. Thus, 3 very similar structural genes appear to exist for the protein I species known to date, and that for Ic normally is silent. Introduction of a functional Ic locus into a Ia+ Ib+ strain caused expression of all three proteins with a reduced rate of synthesis of protein Ia.

Bacterial Proteins↗
PubMed1978

Mutants (ompA) affecting a major outer membrane protein of Escherichia coli K12.

Seventy independent mutants have been analyzed affecting a major protein, polypeptide II, of the outer cell envelope membrane from Escherichia coli K12. They were classified as nonsense mutants of the amber type (20%), mutants most likely of the missense type possessing the protein at normal concentrations (9%), and mutants either missing the protein or harboring it at much reduced concentrations for unknown reasons (71%). Forty of the mutants were analyzed genetically and all were found to map at or near ompA, the structural gene for protein II. Two-dimensional electrophoretic analyses of envelopes from such mutants revealed an unusual heterogeneity of the protein which on such patterns appeared as at least 12 well separated spots, and the majority of these is due to artifacts of the method but apparently specific for this protein. In no case was a polypeptide fragment found in envelopes from the nonsense mutants. The results are discussed regarding two different phages which use the protein as a receptor and concerning the biosynthetic incorporation of the protein into the outer membrane.

Cell Membrane↗
PubMed1978

Cell envelope and shape of Escherichia coli: multiple mutants missing the outer membrane lipoprotein and other major outer membrane proteins.

Starting with an Escherichia coli strain missing the outer membrane lipoprotein, multiple mutants were constructed than in addition to this defect miss the outer membrane proteins II, Ia and Ib, or Ia, Ib, and II. In contrast to all single mutants or strains missing the lipoprotein and polypeptides Ia and Ib, drastic influences on the integrity of the outer membrane and cell morphology were observed in mutants without lipoprotein and protein II. Such strains exhibited spherical morphology. They required increased concentrations of electrolytes for optimal growth, and Mg2+ or Ca2+ were the most efficient. These mutants were sensitive to hydrophobic antibiotics and detergents. Electron microscopy revealed abundant blebbing of the outer membrane, and it could clearly be seen that the murein layer was no longer associated with the outer membrane.

Anti-Bacterial Agents↗
PubMed1978

Bypass of receptor-mediated resistance to colicin E3 in Escherichia coli K-12.

Colicin E3 was found to kill, under conditions of osmotic shock, cells lacking a functional outer membrane receptor (bfe). Under such conditions, component A of the colicin, carrying endonucleolytic activity, also killed bfe cells, whereas fragment T2, obtained by tryptic digestion of the colicin and also active endonucleolytically, was inactive. Tolerance to the colicin caused by defects in the outer membrane could be overcome by osmotic shock, whereas tolerance probably caused by an altered plasma membrane could not.

Cell Membrane↗
PubMed1978

Major proteins of the Escherichia coli outer cell envelope membrane. Sequence of the cyanogen bromide fragments of protein I from Escherichia coli B/r.

The sequence of the cyanogen bromide fragments of one of the major outer membrane proteins of E. coli B/r has been established with the aim of elucidating the primary structure of this protein. Separation of all fragments on one molecular sieve column was achieved upon citraconylation of these fragments. Overlapping peptides were obtained by digestion of the protein, or a cyanogen bromide fragment arising from incomplete cleavage, with trypsin or Staphylococcus aureus protease.

Amino Acid Sequence↗