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Biomedical subjects

B Kenny

Publications and source records attributed to B Kenny.

48 records · Page 3Linked to original sources
PubMed1990

The mechanism of secretion of hemolysin and other polypeptides from gram-negative bacteria.

In the secretion of polypeptides from Gram-negative bacteria, the outer membrane constitutes a specific barrier which has to be circumvented. In the majority of systems, secretion is a two-step process, with initial export to the periplasm involving an N-terminal signal sequence. Transport across the outer membrane then involves a variable number of ancillary polypeptides including both periplasmic and outer membrane. While such ancillary proteins are probably specific for each secreted protein, the mechanism of movement across the outer membrane is unknown. In contrast to these systems, secretion of the E. coli hemolysin (HlyA) has several distinctive features. These include a novel targeting signal located within the last 50 or so C-terminal amino acids, the absence of any periplasmic intermediates in transfer, and a specific membrane-bound translocator, HlyB, with important mammalian homologues such as P-glycoprotein (Mdr) and the cystic fibrosis protein. In this review we discuss the nature of the HlyA targeting signal, the structure and function of HlyB, and the probability that HlyA is secreted directly to the medium through a trans-envelope complex composed of HlyB and HlyD.

Amino Acid Sequence↗
PubMed1989

Fetal brain tissue.

Explore the source record for details and available documents.

Abortion, Induced↗
PubMed1989

Juvenile nasopharyngeal angiofibroma in a static population: the implications of misdiagnosis.

We present a 20-year review of juvenile angiofibroma in the relatively static population of Northern Ireland. Seventeen cases were identified and new slides were prepared from the stored paraffin blocks of all their original biopsy material, and re-examined. Five females, a 36-year-old and an 18-year-old male had their diagnoses revised. We suggest clinical criteria, which in conjunction with radiological investigations, should be strictly applied in all cases. Such application would, in retrospect, have identified those cases excluded by pathological re-examination, thus avoiding unnecessary surgery and radiotherapy. Atypical cases which do not satisfy the clinical criteria may be subjected to repeat biopsy but routine initial biopsy is not recommended.

Adolescent↗
PubMed1989

A novel C-terminal signal sequence targets Escherichia coli haemolysin directly to the medium.

Escherichia coli haemolysin (HlyA), a 107K (K = 10(3) Mr) protein, is secreted to the medium in an hlyB, hlyD-dependent process. Secretion, however, depends on neither an N-terminal signal sequence nor on SecA, which is part of the normal cellular export machinery for periplasmic and outer membrane proteins. In contrast, HlyA contains a novel C-terminal secretion signal encompassing the last 27 amino acids and possibly some additional residues immediately upstream. This region is characterized by a 16 residue 'aspartic acid box' composed largely of small amino acids which we propose constitutes an important element in recognition of the membrane translocation complex constituted by HlyB and HlyD. This feature is also found at the C-terminus of the adenyl cyclase and leukotoxin A molecules and resembles a recently identified eukaryotic C-terminal signal for targeting to glycosomes. A domain of the HlyB component of the haemolysin transport system is also similar to a domain widely distributed in nature, apparently acting as an ATP-dependent transport protein for a wide variety of molecules. Secretion of haemolysin, however, is the first example of a protein translocation system involving an HlyB-like molecule. This suggests that a major role of HlyB or at least its C-terminal domain is the coupling of energy to translocation of the haemolysin. It is more likely therefore that HlyD is more involved in the actual translocation through the membrane. On the basis of genetical and biochemical studies we propose that the haemolysin is translocated directly to the medium bypassing the periplasm. We further propose that HlyB and HlyD together constitute a membrane-bound translocator specific for molecules bearing the HlyA targeting sequence, and that the organization of this complex (conceivably involving other E. coli membrane proteins) must somehow straddle the inner and outer membranes. Finally, the HlyA C-terminal domain has been successfully used to promote the secretion to the medium of a number of heterologous polypeptides, in an HlyB,D-dependent manner.

Amino Acid Sequence↗
PubMed1977

Investigation of adhesive properties of dental composite materials using an improved tensile test procedure and scanning electron microscopy.

A standardized tension test was used to evaluate the adhesive properties of several composite materials when used on both dentin and enamel specimens. The nature of the test surfaces was examined by roughness tests using a Talysurf machine and also in more detail by means of a scanning electron microscope. Poor results were obtained for the adhesion of composite materials to dentin whereas good retention to enamel was obtained.

Adhesiveness↗
PubMedDate not supplied

Haemolysin secretion from E coli.

Haemolysin (HlyA) secretion from E coli is directed by a specific C-terminal targeting signal, located within the last 27-50 amino acids, with quite novel characteristics. The HlyA molecule is secreted directly to the medium without a periplasmic intermediate or detectable proteolytic processing. The C-terminal domain of HlyA can also be used to promote the secretion of several other E coli and mammalian proteins. HlyD and HlyB are essential for translocation of HlyA to the medium and we propose that these proteins form a transenvelope complex which initially binds the HlyA signal followed by transport of HlyA to the medium. HlyB is a member of a family of membrane proteins engaged in ATP dependent secretion mechanisms conserved in many organisms including man (P-glycoprotein and the CF protein). In this review we discuss the structure, function and regulation of the secretion mechanism.

Amino Acid Sequence↗