Acyl carrier proteins (ACPs) are essential to the production of fatty acids. In some species of marine bacteria, ACPs are arranged into tandem repeats joined by peptide linkers, an arrangement that results in high fatty acid yields. By contrast, Escherichia coli, a relatively low producer of fatty acids, uses a single-domain ACP. In this work, we have engineered the native E. coli ACP into tandem di- and tri-domain constructs joined by a naturally occurring peptide linker from the PUFA synthase of Photobacterium profundum. The size of these tandem fused ACPs was determined by size exclusion chromatography to be higher (21 kDa, 36 kDa and 141 kDa) than expected based on the amino acid sequence (12 kDa, 24 kDa and 37 kDa, respectively) suggesting the formation of a flexible extended conformation. Structural studies using small-angle X-ray scattering (SAXS), confirmed this conformational flexibility. The thermal stability for the di- and tri-domain constructs was similar to that of the unfused ACP, indicating a lack of interaction between domains. Lastly, E. coli cultures harboring tandem ACPs produced up to 1.6 times more fatty acids than wild-type ACP, demonstrating the viability of ACP fusion as a method to enhance fatty acid yield in bacteria.

The biosynthesis of polyunstaurated fatty acids (PUFA) in certain bacterial species, is regulated by processes that are not fully understood. One possible factor in the modulation of gene expression in PUFA biosynthesis is pfaR, a putative transcriptional regulator whose gene is encoded directly upstream of pfaA in some bacterial species but entirely absent in others. Here we report the expression of pfaR in Escherichia coli together with its purification by Ni2+ affinity chromatography. Our results show that the majority of pfaR is produced as an insoluble protein that can be reconstituted from inclusion bodies. After inclusion body reconstitution, pfaR remains amenable for affinity purification. Additional bioinformatics analyses indicate the presence of a conserved winged helix‐turn‐helix (wHTH) domain flanked by a number of conserved motifs which include a predicted protein‐protein interaction site. Sequence alignments and motif structure analyses reveal evolutionary divergence in this family of transcriptional regulators, consistent with the likely DNA‐binding function of pfaR. Currently, we are in the process of analyzing pfaR secondary structure using circular dichroism. Future work will include functional analysis using systematic evolution of ligands by exponential enrichment.Support or Funding InformationThis work was supported by the National Institutes of Health [R25 GM061838, R25GM061151‐ 15, 5T34GM007821‐37, T36‐GM‐095335]; and the NationalScience Foundation [CHE0953254].This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.