Biomedical subjects
S Brewer
Publications and source records attributed to S Brewer.
Structure and function of X-Pro dipeptide repeats in the TonB proteins of Salmonella typhimurium and Escherichia coli.
The TonB protein is required for several outer membrane transport processes in bacteria. A short 33-residue peptide segment of TonB has been studied by 1H and 13C nuclear magnetic resonance spectroscopy. The sequence of this peptide segment contains multiple Glu-Pro and Lys-Pro dipeptide repeats that maintain rigid, elongated structures and flank a short connecting segment that adopts a beta-strand configuration. This TonB peptide is shown to interact specifically with the FhuA protein, the outer membrane receptor for ferrichrome-iron, providing the first direct evidence that the TonB protein interacts with outer membrane receptors. Interaction with the FhuA protein involves the extended structural element containing positively charged Lys-Pro repeats, and suggests a functional role for this segment of the TonB protein. As TonB is anchored in the cytoplasmic membrane the protein must, uniquely, span the periplasm. These data, together with studies described in the accompanying paper, suggest a model by which TonB serves to transduce conformational information over extended distances, from the cytoplasmic membrane to the outer membrane.
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The nature of arterial healing following dextran treatment of experimental small artery trauma.
Vascular thrombosis is a major cause of morbidity and death. Because of the many variables involved with thrombosis in patients, major advances in treatment often depend upon design and study of adequate experimental models which provide a degree of control of the variables. Arterial trauma was produced in small femoral arteries 3 mm. or less in diameter by a standardized intimectomy technique. One group of animals was treated with an equal volume of saline and served as controls. Serial sections of blood vessels at graded time intervals from one hour to 90 days were studied. The damaged blood vessels of dextran-treated animals did not thrombose and provided an opportunity for studying the mechanism of healing in traumatized blood vessels which remained patent. The damaged blood vessels of saline-treated animals uniformly thrombosed and eventually healed for scar formation with evidences of attempts at recanalization. The blood vessels of dextran-treated animals remained open for as long as 90 days and were re-endothelialized and healed. What appears to be beginning re-endothelialization of blood vessels of dextran-treated animals was observed as early as 48 hours. In a model experimental setting, dextran has been shown to prevent thrombosis and permit healing in small arteries subjected to a standardized surgical trauma.