title: Structure and Function of Cyanobacterial DHDPS and DHDPR.
abstract: Lysine biosynthesis in bacteria and plants commences with a condensation reaction catalysed by dihydrodipicolinate synthase (DHDPS) followed by a reduction reaction catalysed by dihydrodipicolinate reductase (DHDPR). Interestingly, both DHDPS and DHDPR exist as different oligomeric forms in bacteria and plants. DHDPS is primarily a homotetramer in all species, but the architecture of the tetramer differs across kingdoms. DHDPR also exists as a tetramer in bacteria, but has recently been reported to be dimeric in plants. This study aimed to characterise for the first time the structure and function of DHDPS and DHDPR from cyanobacteria, which is an evolutionary important phylum that evolved at the divergence point between bacteria and plants. We cloned, expressed and purified DHDPS and DHDPR from the cyanobacterium Anabaena variabilis. The recombinant enzymes were shown to be folded by circular dichroism spectroscopy, enzymatically active employing the quantitative DHDPS-DHDPR coupled assay, and form tetramers in solution using analytical ultracentrifugation. Crystal structures of DHDPS and DHDPR from A. variabilis were determined at 1.92 Å and 2.83 Å, respectively, and show that both enzymes adopt the canonical bacterial tetrameric architecture. These studies indicate that the quaternary structure of bacterial and plant DHDPS and DHDPR diverged after cyanobacteria evolved.
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia.
authors.forename: Janni B
authors.initials: JB
authors.lastname: Christensen
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia.
authors.forename: T P
authors.initials: TP
authors.lastname: Soares da Costa
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia.
authors.forename: Pierre
authors.initials: P
authors.lastname: Faou
authors.affiliation: Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, Christchurch 8140, New Zealand.
authors.forename: F Grant
authors.initials: FG
authors.lastname: Pearce
authors.affiliation: Australian Synchrotron, Clayton, Victoria 3168, Australia.|Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Santosh
authors.initials: S
authors.lastname: Panjikar
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Perugini
mesh_terms: D046870:Anabaena variabilis / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D050746:Dihydrodipicolinate Reductase / Q000737:chemistry* / Q000235:genetics; D006836:Hydro-Lyases / Q000737:chemistry* / Q000235:genetics; D020836:Protein Structure, Quaternary; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D050746:Dihydrodipicolinate Reductase; D006836:Hydro-Lyases; C020040:4-hydroxy-tetrahydrodipicolinate synthase