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Biomedical subjects

M G Schmidt

Publications and source records attributed to M G Schmidt.

7 recordsLinked to original sources
PubMed1991

Regulation of Escherichia coli secA mRNA translation by a secretion-responsive element.

The Escherichia coli secA gene, whose translation is responsive to the proficiency of protein export within the cell, is the second gene in a three-gene operon and is flanked by gene X and mutT. By using gene fusion and oligonucleotide-directed mutagenesis techniques, we have localized this translationally regulated site to a region at the end of gene X and the beginning of secA. This region has been shown to bind SecA protein in vitro. These studies open the way for a direct investigation of the mechanism of secA regulation and its coupling to the protein secretion capability of the cell.

Adenosine Triphosphatases↗
PubMed1989

SecA protein autogenously represses its own translation during normal protein secretion in Escherichia coli.

The Escherichia coli secA gene, whose expression is responsive to the protein secretion status of the cell, is the second gene in an operon. We found that both the basal and induced levels of SecA biosynthesis are dependent on prior translation of the upstream gene, gene X, and identified two large gene X-secA transcripts. The 10-fold derepression of secA expression by protein export defects was at the translational level since no further increases in gene X or secA mRNA levels were detected during this period, and a secA-lacZ protein fusion but not an operon fusion was appropriately derepressed. Furthermore, overexpression of the SecA protein severely reduced expression of only the secA-lacZ protein fusion, indicating that SecA autogenously represses its own translation.

Bacterial Proteins↗
PubMed1988

Nucleotide sequence of the secA gene and secA(Ts) mutations preventing protein export in Escherichia coli.

The DNA sequence of the secA gene, essential for protein export in Escherichia coli, was determined and found to encode a hydrophilic protein of 901 amino acid residues with a predicted molecular weight of 101,902, consistent with its previously determined size and subcellular location. Sequence analysis of 9 secA(Ts) mutations conferring general protein export and secA regulatory defects revealed that these mutations were clustered in three specific regions within the first 170 amino acid residues of the SecA protein and were the result of single amino acid changes predicted to be severely disruptive of protein structure and function. The DNA sequence immediately upstream of secA was shown to encode a previously inferred gene, gene X. Sequence analysis of a conditionally lethal amber mutation, am109, previously inferred to be located proximally in the secA gene, revealed that it was located distally in gene X and was conditionally lethal due to its polar effect on secA expression. This and additional evidence are presented indicating that gene X and secA are cotranscribed.

Amino Acid Sequence↗
PubMed1979

Patient as volunteer: an assault on chronicity.

By integrating selected former patients into its regular volunteer program, a South Australian state hospital reduced the hospital stays and the readmissions of a large number of the participants who had previously been seen as failures of the community mental health movement. The author describes the program, its benefits, and some limitations and problems, such as an occasional extra burden on ward personnel. The former patients' new roles as volunteers enabled them to get the support they needed from the hospital but through means more acceptable to them. The program also improved their self-esteem and enabled them to engage in more normalizing social relationships.

Adult↗
PubMed1976

Strain-related differences in immunosuppressive effects of Enterobacteriaceae and their lipopolysaccharides on production in rabbits of antibody to enterobacterial common antigen.

Certain polysaccharides have been shown to inhibit the antibody response of rabbits to the common enterobacterial antigen (CA). The present investigation revealed that striking differences exist in the immunosuppressive effects of enteric bacteria and their lipolysaccharides (lps), depending upon CA production by the strains. Mixtures of immunogenic strains (Escherichia coli F2378 [R4], E. coli F470 [R1], or Shigella boydii F3140 [R]) and non-immunogenic CA-producing strains, such as E. coli O1, E. coli O113, Salmonella montevideo, and S. minnesota, as well as the R mutants E. coli F614 (R1), E. coli F757 (R1), and S. typhimurium his 642 (Ra), failed to elicit CA antibodies. In contrast, mixtures of the immunogen and CA-negative strains S. typhimurium his 386 (Ra) and S. minnesota P595 (Re) or R555 (Ra) yielded antibodies in titers similar to those elicited by the immunogen alone. Further, LPS of CA-positive but not of CA-negative strains exerted this immunosuppressive effect. Quantitative studies revealed that LPS of S. minnesota in amounts of 100 mug/ml was strongly immunosuppressive, in amounts of 20 mug/ml slightly effective, and in amounts of 4 mug/ml ineffective. It is postulated that hitherto unknown differences exist, either in composition or in configuration, between LPS obtained from different microorganisms to account for the strain-related differences in immunosuppressive effects and, further, that the immunosuppressive LPS interacts with immunogenic CA.

Animals↗