Submitted to: Coccidiosis International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 8, 2005
Publication Date: September 19, 2005
Citation: Allen, P.C., Miska, K.B., Jenkins, M.C., Fetterer, R.H. 2005. Acetyl coa carboxylase in avian eimeria. Coccidiosis International Conference Proceedings. p. 164.
Acetyl coA carboxylase, catalyzes the first committed step in the biosynthesis of fatty acids. In some apicomplexan parasites such as Toxoplasma gondii and Plasmodium sp., a multi-domain form of this enzyme (ACC 1) has been identified as a nuclear-encoded protein that is transported to and apparently functions in the apicoplast organelle found in zoite stages of parasites life cycles. The unique genetic origin of this enzyme and its apparent requirement for parasite development suggests its potential as a target for control of apicomplexan parasites. We have therefore undertaken the characterization of this enzyme in avian Eimeria. BLAST searches of both nucleotide and protein data files from T. gondii ACC1 (tACC1) precursor against the Sanger Eimeria tenella data base have found the orthologous Eimeria ACC1 (eACC1) gene to be contained in Contig 5754, and the carbamyl phosphate synthase, (5’end), biotin binding, and carboxyl transferase (3’ end) domains have been identified both through bioinformatics searches and PCR. The low genetic complexity of the central portion of the eACC1 gene has made its complete sequencing difficult. A 224 nt sequence that is 73 nt upstream from the first exon common to tACC1 and eACC1 has been identified as a possible signal sequence for eACC1. However, no tripartite leader sequence such as found in tACC1 precursor, that would allow transport of the protein into an apicoplast, has been defined. These observations, along with the lack of evidence for an Eimerian apicoplast in the ultrastructure literature, suggest major differences between tACC1 and eACC1. Expression of eACC1 protein has been documented through detection on polyacrylamide gels of a biotin-containing protein band of about 250 kd. On a protein basis, this band appears most intense in merozoite extracts as compared to extracts of oocysts and sporozoites. Determinations of differential gene and protein expression of eACC1 among separate Eimeria species and stages of development are ongoing through use of RT-PCR and Western blots of extracts.