Biomedical subjects

A Pugsley

Publications and source records attributed to A Pugsley.

3 recordsLinked to original sources

PubMed1997

ActA is a dimer.

ActA, a surface protein of Listeria monocytogenes, is able to induce continuous actin polymerization at the rear of the bacterium, in the cytosol of the infected cells. Its N-terminal domain is sufficient to induce actin tail formation and movement. Here, we demonstrate, using the yeast two-hybrid system, that the N-terminal domain of ActA may form homodimers. By using chemical cross-linking to explore the possibility that ActA could be a multimer on the surface of the bacteria, we show that ActA is a dimer. Cross-linking experiments on various L. monocytogenes strains expressing different ActA variants demonstrated that the region spanning amino acids 97-126, and previously identified as critical for actin tail formation, is also critical for dimer formation. A model of actin polymerization by L. monocytogenes, involving the ActA dimer, is presented.

Bacterial Proteins↗

PubMed1987

Symptoms, atopy, and bronchial response to methacholine in parents with asthma and their children.

We have studied 50 children with one parent with asthma at a mean age of 6.4 years by symptom questionnaire and performed allergy skin testing and measurement of bronchial responsiveness to methacholine in both parent and child in 29-32 cases. Ninety eight per cent of the parents were receiving medication for asthma. Fifty one per cent had visited their doctor and 20% had taken more than five days off work in the previous 12 months; 12% had been admitted to hospital during the preceding 10 years. In the children the prevalences of wheeze, shortness of breath, and cough were all about double that found in a general population survey of children of similar age. Atopy was present in 90% of parents, but the prevalence of atopy among the children was not significantly different from the children in the general population. Eczema and hay fever, however, had high prevalences of 40% and 24%, respectively. Responsiveness to methacholine (provocation dose achieving 20% fall in forced expiratory volume in one second less than 6.4 mumol) was found in 93% of parents and 45% of children, which is compatible with a large increase compared with the general population. All atopic but only 50% of non-atopic children with symptoms of asthma responded to methacholine. These findings indicate that children who have one parent with asthma have roughly double the chance of developing clinical features of asthma compared with the general population and suggests that, in these children, a causal interaction occurs between atopy and bronchial hyper-responsiveness.

Asthma↗

PubMed1980

Correlation between the expression of an Escherichia coli cell surface protein and the ability of the protein to bind to lipopolysaccharide.

The ompA gene of Escherichia coli codes for a major protein of the outer membrane. When this gene was moved between various unrelated strains (E. coli K-12 and two clinical isolates of E. coli) by transduction, the gene was expressed very poorly. Recombinants carrying "foreign" genes produced no OmpA protein which could be detected on polyacrylamide gels and became resistant to bacteriophage K3, which uses this protein as receptor. The recombinants were sensitive to host-range mutants of K3, indicating a very low level of OmpA protein was produced. When an E. coli K-12 recombinant carrying an unexpressed foreign ompA allele was subjected to two cycles of selection for an OmpA(+) phenotype, a mutant strain was obtained which was sensitive to K3 and which expressed nearly normal levels of OmpA protein in the outer membrane. This strain carried mutations in the foreign ompA gene, as indicated both by genetic mapping and the alteration of a peptide in the mutant OmpA protein. The ability of the OmpA protein to bind to lipopolysaccharide (LPS) showed similar strain specificity, and the mutant OmpA protein which was expressed in an unrelated host showed enhanced ability to bind LPS from its new host. Thus, cell surface expression of the ompA gene appears to depend upon the ability of the gene product to bind LPS, suggesting that an interaction between the protein and LPS plays an essential role in biosynthesis of this outer membrane protein.

Bacterial Proteins↗