Linked genes for calmodulin and E2 ubiquitin-conjugating enzyme in Trichomonas vaginalis

In searching the genomes of early-diverging protists to study whether the possession of calmodulin is ancestral to all eukaryotes, the gene for calmodulin was identified in Trichomonas vaginalis. This flagellate is a member of the Parabasalia, one of the earliest lineages of recognized eukaryotes to have diverged. This sequence was used to isolate a homologous 1.250-kb fragment from the T. vaginalis genome by inverse polymerase chain reaction. This fragment was also completely sequenced and shown to contain the 3' end of the single-copy calmodulin gene and the 3' end of a gene encoding a protein with high similarity to E2 ubiquitin-conjugating enzymes, a family which has previously only been identified in animals, plants, and fungi. Phylogenetic analysis of 50 members of the E2 family distinguishes at least nine separate subfamilies one of which includes the T. vaginalis E2-homologue and an uncharacterized gene from yeast chromosome XII.

Stable-isotope studies of glutamate catabolism in Fusobacterium nucleatum

Catabolism of glutamate was investigated in Fusobacterium nucleatum, an anaerobic micro-organism that is strongly implicated in periodontal disease. The distribution of labels in acetate and butyrate derived from [13C]glutamates was determined by NMR spectroscopy and MS. The label from L-[5-13C]glutamate was not incorporated, whereas C-1 of acetate and butyrate were efficiently labelled by L-[1-13C]glutamate; these results indicated that the hydroxyglutarate pathway predominated. In butyrate, enrichment at C-3 was smaller than C-1; that this was not due to participation of the methylaspartate pathway was demonstrated by the incorporation of label from L-[4-13C]glutamate into only C-2 of acetate and C-4 (major)/C-2 (minor) of butyrate. The presence of label at a second site in butyrate was attributed to the synthesis of butyrate from acetate and verified by the incorporation of label from [1,2-13C2]- and [2H3]-acetate.