Quantitative decarboxylation of (14C) amino acids using automatic amino acid analyzer.
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Amino Acids↗
Biomedical subjects
N W Charon
Publications and source records attributed to N W Charon.
Antileptospiral activity in lower-vertebrate sera.
Normal serum from the painted turtle (Chrysemys picta), the snapping turtle (Chelydra serpentina), and the frog (Rana pipiens) were found to possess bactericidal activity towards Leptospira. Leptospires from both the parasitic and biflexa complexes were killed by these sera at high dilutions. This pattern differs from that of mammalian serum, as generally only the biflexa complex leptospires are killed by normal mammalian serum. The activity in C. picta serum was characterized as being complement dependent and not mediated by basic proteins. Because comple-inactivated C. picta serum regained leptospiricidal activity after the addition of fresh rabbit serum, antibody is also likely to participate in the killing activity. Further support that C. picta serum contained leptospiral antibodies was found by the detection of serotype-specific agglutinins.
Animals↗
Amino acid biosynthesis in the spirochete Leptospira: evidence for a novel pathway of isoleucine biosynthesis.
Radioactive carbon dioxide was incubated with growing cells of Leptospira interrogans serotypes semaranga and tarassovi, and the specific activities and distribution of the label within the cellular amino acids were determined. The origins of the carbon skeletons of all the acid-stable amino acids except isoleucine were found to be consistent with known biosynthetic pathways for these amino acids. Experiments using radioactive carbon dioxide and other tracers indicated that most of the isoleucine was synthesized by a pathway not involving threonine. The origin of the carbon skeleton of isoleucine consisted of two residues of pyruvate (carbons 2 and 3) and acetate of acetyl-coenzyme A by this pathway. Isotope competition studies indicated that the pathway was regulated by isoleucine. The results are discussed in relation to two proposed pathways of isoleucine biosynthesis involving citramalate as an intermediate.
Amino Acids↗
Spirochete chemotaxis, motility, and the structure of the spirochetal periplasmic flagella.
Spirochetes have a unique motility system that is characterized by flagellar filaments contained within the outer membrane sheath. Direct evidence using video microscopy has recently been obtained which indicates that these periplasmic flagella (PF) rotate in several spirochetal species. This rotation generates thrust. As shown for one spirochete, Spirochaeta aurantia, motility is driven by a proton motive force. Spirochete chemotaxis has been most thoroughly studied in S. aurantia. This spirochete exhibits three distinct behaviours, runs of smooth swimming, reversals and flexing. These behaviours are modulated by addition of attractants such that S. aurantia swims towards higher concentrations of attractants in a spatial gradient. Unlike the prototypical bacterium, Escherichia coli, chemotaxis in S. aurantia involves fluctuations in membrane potential. The PF of a number of spirochetes have been examined in considerable detail. For most species, the PF filaments are complex, consisting of an assembly of several different polypeptides. There are several antigenically related core polypeptides surrounded by an outer layer consisting of a different polypeptide. Borrelia burgdorferi and Spirochaeta zuelzerae represent exceptions where the filaments are composed of a single major polypeptide species. The genes encoding the filament polypeptides from several spirochete species have been cloned and analysed. Apparently, the outer layer polypeptides of S. aurantia, Treponema pallidum and Serpulina hyodysenteriae are transcribed from sigma-70-like promoters, whereas the core polypeptide genes are transcribed from sigma-28-like promoters. A gene encoding the hook polypeptide in Treponema phagedenis has been cloned and analysed. The product of this gene shows significant similarity to the E. coli hook protein, FlgE, and homologs have been identified in T. pallidum and B. burgdorferi.(ABSTRACT TRUNCATED AT 250 WORDS)
Borrelia burgdorferi Group↗