Molecular analysis of a Type I fatty acid synthase in Cryptosporidium parvum

We report here the molecular analysis of a Type I fatty acid synthase in th e apicomplexan Cryptosporidium parvum (CpFAS1). The CpFAS1 gene encodes a m ultifunctional polypeptide of 8243 amino acids that contains 21 enzymatic d omains. This CpFAS1 structure is distinct from that of mammalian Type I FAS , which contains only seven enzymatic domains. The CpFAS1 domains are organ ized into: (i) a starter unit consisting of a fatty acid ligase and an acyl carrier protein: (ii) three modules, each containing a complete set of six enzymes (acyl transferase, ketoacyl synthase: ketoacyl reductase. dehydras e, enoyl reductase, and acyl carrier protein) for the elongation of fatty a cid C2-units: and (iii) a terminating domain whose function is as yet unkno wn. The CpFAS1 gene is expressed throughout the life cycle of C. parvum, si nce its transcripts and protein were detected by RT-PCR and immunofluoresce nt localization, respectively. This cytosolic Type I CpFAS1 differs from th e organellar Type II FAS enzymes identified from Toxoplasma gondii and Plas modium falciparum which are targetted to the apicoplast, and are sensitive to inhibition by thiolactomycin. That the discovery of CpFAS1 may provide a new biosynthetic pathway for drug development against cryptosporidiosis, i s indicated by the efficacy of the FAS inhibitor cerulenin on the growth of C. parvum in vitro. (C) 2000 Published by Elsevier Science B.V. All rights reserved.