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PubMed1968

Electron transport in mitochondria isolated from the flagellate Polytomella caeca.

1. Mitochondria isolated from Polytomella caeca contain cytochromes b, c+c(1) and a+a(3) and several flavoprotein species. 2. Electron transport is inhibited by antimycin A, rotenone, piericidin A and cyanide. 3. Spectral data indicate that antimycin A inhibits the reoxidation of reduced cytochrome b. 4. Various types of flavoprotein are characterized by simultaneous spectrophotometric and fluorimetric measurements on antimycin A-inhibited preparations and also by their absorption and fluorescence-emission spectra. 5. The rotenone-sensitive site lies between the two flavoproteins of the respiratory chain, designated FpD1 and FpD2. 6. Other flavoprotein species detected include those involved in the oxidation of succinate and externally added NADH; a large proportion of mitochondrial flavine is reduced by dithionite but not by known respiratory substrates. 7. The kinetics of flavoprotein and cytochrome reactions were studied.

Journal Article↗
PubMed1968

Propionate assimilation in the flagellate Polytomella caeca. An inducible mitochondrial enzyme system.

1. The assimilation of propionate by Polytomella caeca involves the beta-oxidation of this fatty acid. 2. Propionate-grown cells immediately oxidize propionate, beta-hydroxypropionate, malonic semialdehyde and acetate; acetate-grown cells oxidize propionate rapidly only after a lag of 2hr., and this adaptation of resting cells to propionate involves the formation of the enzymes of beta-oxidation. 3. The beta-hydroxypropionate dehydrogenase and malonic semialdehyde dehydrogenase activities of both propionate-grown and propionate-adapted cells are partly located in mitochondrial fractions. 4. Mitochondria isolated from propionate-grown cells, and also those from acetate-grown cells fully adapted to propionate, oxidize succinate, alpha-oxoglutarate, beta-hydroxypropionate and malonic semialdehyde; oxidation of these substrates is tightly coupled to the phosphorylation of ADP. 5. Mitochondria from acetate-grown cells exhibit ADP-dependent oxidation of succinate and alpha-oxoglutarate, but do not oxidize beta-hydroxypropionate or malonic semialdehyde. Mitochondria isolated from acetate-grown cells adapted to propionate for 5hr. slowly oxidize beta-hydroxypropionate and malonic semialdehyde, but no tightly coupled phosphorylation is detectable. 6. Two of the inducible enzymes of propionate oxidation are located within the NAD-impermeable barrier and appear to be membrane-bound. 7. The formation of the inducible enzymes is inhibited by cycloheximide and actinomycin D, but not by chloramphenicol.

Acetates↗
PubMed2005

Evasion of Toll-like receptor 5 by flagellated bacteria.

Toll-like receptor 5 (TLR5) recognizes an evolutionarily conserved site on bacterial flagellin that is required for flagellar filament assembly and motility. The alpha and epsilon Proteobacteria, including the important human pathogens Campylobacter jejuni, Helicobacter pylori, and Bartonella bacilliformis, require flagellar motility to efficiently infect mammalian hosts. In this study, we demonstrate that these bacteria make flagellin molecules that are not recognized by TLR5. We map the site responsible for TLR5 evasion to amino acids 89-96 of the N-terminal D1 domain, which is centrally positioned within the previously defined TLR5 recognition site. Salmonella flagellin is strongly recognized by TLR5, but mutating residues 89-96 to the corresponding H. pylori flaA sequence abolishes TLR5 recognition and also destroys bacterial motility. To preserve bacterial motility, alpha and epsilon Proteobacteria possess compensatory amino acid changes in other regions of the flagellin molecule, and we engineer a mutant form of Salmonella flagellin that evades TLR5 but retains motility. These results suggest that TLR5 evasion is critical for the survival of this subset of bacteria at mucosal sites in animals and raise the intriguing possibility that flagellin receptors provided the selective force to drive the evolution of these unique subclasses of bacterial flagellins.

Amino Acid Sequence↗