Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/23/2015
Publication Date: N/A
Technical Abstract: Using a complementation assay in E. coli, we have shown that the propionyl-CoA carboxylase complex (PCC) from Wolbachia pipientis wMel, order Rickettsiales, provides for lipid biosynthesis through malonyl-CoA production. Normally, the prototypical prokaryote fatty acid synthesis (FASII) initiation module functions to produce the primer and building blocks, malonyl-CoA, to feed the elongation model. Acetyl-CoA carboxylase (ACC) performs this first step to generate malonyl-CoA, from the carboxylation of acetyl-CoA. ACC is an almost ubiquitous enzyme system consisting of a multisubunit complex of AccC (biotin carboxylase), AccB (biotin carboxyl carrier protein), and AccA and AccD (a carboxyltransferase). The Rickettsiales lack ACC, although those that have been sequenced encode two genes, pccA and pccB, encoding for the PCC. Typically the PCC carboxylates propionyl-CoA into (S)-methylmalonyl-CoA. However, metabolomics predicts that propionyl-CoA is not synthesized in the Rickettsiales and there is no identifiable use for (S)-methylmalonyl-CoA. Functionally PCC is similar to ACC in that it consists of a biotin carboxylase and biotin carboxyl carrier protein (PccA) and a carboxyltransferase (PccB). Considering that Rickettsiales lack ACC and there is no clear pathway for synthesizing malonyl-CoA, does the PCC complex provide the functional activity? We utilized an ACC conditionally lethal strain of E. coli that carries an inducible plasmid harboring accBC to produce malonyl-CoA. Replacement of the accBC plasmid with one carrying wMel pccAB complements for the absence of malonyl-CoA. This confirms that the wMel PCC produces malonyl-CoA. Furthermore, qRT-PCR was performed and transcripts for both pccA and pccB were confirmed in actively growing MOS55 cell culture infected with wMel. These discoveries suggest the rickettsial cell produces malonyl-CoA through the non-traditional PCC demonstrating that the bacterium is fully capable of intrinsic lipid biosynthesis. With this confirmation preliminary drug susceptibility testing in E. coli suggests that the PCC may make an ideal target in the Rickettsiales.