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Mechanism Of Abietadiene Synthase Catalysis: Stereochemistry And Stabilization Of The Cryptic Pimarenyl Carbocation Intermediates, Reuben J. Peters, Matthew M. Ravn, Robert M. Coates, Rodney Croteau
Mechanism Of Abietadiene Synthase Catalysis: Stereochemistry And Stabilization Of The Cryptic Pimarenyl Carbocation Intermediates, Reuben J. Peters, Matthew M. Ravn, Robert M. Coates, Rodney Croteau
Reuben J. Peters
Abietadiene synthase (AS) catalyzes the complex cyclization-rearrangement of (E,E,E)-geranylgeranyl diphosphate (8, GGPP) to a mixture of abietadiene (1a), double bond isomers 2a-4a and pimaradienes 5a-7a as a key step in the biosynthesis of the abietane resin acid constituents (1b-4b) of conifer oleoresin. The reaction proceeds at two active sites by way of the intermediate, copalyl diphosphate (9). In the second site, a putative tricyclic pimaradiene or pimarenyl(+) carbocation intermediate of undefined C13 stereochemistry and annular double bond position is formed. Three 8-oxy-17-nor analogues of 9 (17 and 19a,b) and three isomeric 15,16-bisnorpimarenyl-N-methylamines (26a-c) were synthesized and evaluated as alternative substrates …
Complement Resistance, As Determined By Viable Count And Flow Cytometric Methods, And Its Association With The Presence Of Iss And The Virulence Of Avian Escherichia Coli, Lisa K. Nolan, Catherine W. Giddings, Shelley M. Horne, Curt Doetkott, Penelope S. Gibbs, Richard E. Wooley, Steven L. Foley
Complement Resistance, As Determined By Viable Count And Flow Cytometric Methods, And Its Association With The Presence Of Iss And The Virulence Of Avian Escherichia Coli, Lisa K. Nolan, Catherine W. Giddings, Shelley M. Horne, Curt Doetkott, Penelope S. Gibbs, Richard E. Wooley, Steven L. Foley
Lisa K. Nolan
Previous work in our labs has shown that avian Escherichia coli virulence is correlated with resistance to complement. Also, our studies have revealed that the presence of the increased serum survival gene (iss), known to contribute to the complement resistance and virulence of mammalian E. coli, may predict the virulent nature of an avian E. coli isolate. This relationship warrants further research, but further clarification of the relationship among virulence, complement resistance, and iss sequences requires use of complement susceptibility assays. Such assays, unfortunately, are labor-intensive, expensive, and difficult to perform. In the present study, the results of two complement …
Location Of Increased Serum Survival Gene And Selected Virulence Traits On A Conjugative R Plasmid In An Avian Escherichia Coli Isolate, Timothy J. Johnson, Catherine W. Giddings, Shelley M. Horne, Penelope S. Gibbs, Richard E. Wooley, Jerod Skyberg, Pam Olah, Ronda Kercher, Julie S. Sherwood, Steven L. Foley, Lisa K. Nolan
Location Of Increased Serum Survival Gene And Selected Virulence Traits On A Conjugative R Plasmid In An Avian Escherichia Coli Isolate, Timothy J. Johnson, Catherine W. Giddings, Shelley M. Horne, Penelope S. Gibbs, Richard E. Wooley, Jerod Skyberg, Pam Olah, Ronda Kercher, Julie S. Sherwood, Steven L. Foley, Lisa K. Nolan
Lisa K. Nolan
Avian colibacillosis is a costly disease for the poultry industry. The mechanisms of virulence employed by the etiologic agent of this disease remain ill defined. However, accumulated evidence suggests that complement resistance and the presence of the increased serum survival gene (iss) in an avian Escherichia coli isolate may be indicative of its ability to cause disease. This association of iss with the E. coli implicated in avian disease may mean that iss and/or, perhaps, the genes associated with it are important contributors to avian E. coli virulence. For this reason, we have begun a search for iss's location in …
Abietadiene Synthase Catalysis: Conserved Residues Involved In Protonation-Initiated Cyclization Of Geranylgeranyl Diphosphate To (+)-Copalyl Diphosphate, Reuben J. Peters, Rodney B. Croteau
Abietadiene Synthase Catalysis: Conserved Residues Involved In Protonation-Initiated Cyclization Of Geranylgeranyl Diphosphate To (+)-Copalyl Diphosphate, Reuben J. Peters, Rodney B. Croteau
Reuben J. Peters
Abietadiene synthase catalyzes two sequential, mechanistically distinct cyclization reactions in the formation of a mixture of abietadiene double bond isomers as the committed step in resin acid biosynthesis. Each reaction is carried out at a separate active site residing in a structurally distinct domain, and the reactions are kinetically separable. The first cyclization reaction is initiated by protonation of the terminal double bond of the universal diterpene precursor, geranylgeranyl diphosphate. The pH dependence of the overall reaction is consistent with an acid-base catalytic mechanism, and a divalent metal ion plays a role in this reaction probably by binding the diphosphate …
Virulence Factors Of Escherichia Coli From Cellulitis Or Colisepticemia Lesions In Chickens, J. S. Jeffrey, Lisa K. Nolan, K. H. Tonooka, S. Wolfe, C. W. Giddings, S. M. Horne, S. L. Foley, A. M. Lynne, J. O. Ebert, L. M. Elijah, G. Bjorklund, S. J. Pfaff-Mcdonough, R. S. Singer, C. Doetkott
Virulence Factors Of Escherichia Coli From Cellulitis Or Colisepticemia Lesions In Chickens, J. S. Jeffrey, Lisa K. Nolan, K. H. Tonooka, S. Wolfe, C. W. Giddings, S. M. Horne, S. L. Foley, A. M. Lynne, J. O. Ebert, L. M. Elijah, G. Bjorklund, S. J. Pfaff-Mcdonough, R. S. Singer, C. Doetkott
Lisa K. Nolan
This study was designed to compare virulence factors of cellulitis-derived Escherichia coli to colisepticemic E. coli in order to clarify whether E. coli associated with cellulitis comprise a unique subset of pathogenic E. coli. Isolates were tested for serotype, capsule, aerobactin production, colicin production, the presence of the iss gene, and serum resistance. Untypable isolates made up the greatest percentage of each group. Serotypes O2 and O78 were the most commonly identified among both groups of isolates. No statistical differences in the distribution of aerobactin or colicin production, capsule, or iss gene were observed between groups. Cluster analysis showed that …