Crystal structure of phosphoenolpyruvate carboxylase from Methylobacterium extorquens

RICARDO MARTI-ARBONA; JAVIER MARCELO GONZALEZ; CLIFF UNKEFER

Albuquerque

Congreso; American Crystallographic Association Annual Meeting 2014; 2014

American Crystallographic Association

Methylobacterium extorquens is a facultative aerobic α-proteobacterium ableto use the Serine Pathway to assimilate reduced one-carbon compounds (C1),like methanol and formaldehyde. During such methylotrophic growth, C1compounds are incorporated into glycine (C2) to produce serine (C3),further metabolized into phosphoenolpyruvate, to render oxaloacetate (C4)through carboxylation with atmospheric CO2. This step is catalyzed by theenzyme PEP carboxylase (PEPC). As a result, M. extorquens has gainedinterest as a biotechnologically relevant microorganism for bioremediationof industrial wastes rich in C1 compounds, particularly methanol, as wellas CO2 fixation as organic matter.Previous kinetic studies of M. extorquens PEPC showed a remarkabletolerance to feedback regulation by C4 dicarboxylic acids (eg. malate,aspartate), leading to an overall higher enzymatic activity. A similarscenario has been witnessed for PEPC from Flaveria trinervia. By comparingPEPC from F. pringlei, which is sensitive to inhibition by C4 dicarboxylicacids, with that of F. trinervia, the mutation Arg884Gly was shown to causethe decreased inhibition. However, PEPC from M. extorquens displays anArg884 residue, suggesting the presence of a different molecular mechanismbehind the reduced inhibition in this enzyme. We solved the crystalstructure of M. extorquens PEPC aiming to unveil the structuraldeterminants for such reduced feedback inhibition. Crystals belong to spacegroup P212121, with unit cell parameters (a, b, c) = (74.42, 228.99,238.21); α, β, γ = 90°. This structure is analyzed in the context ofavailable PEPC structures, in order to get insights into the differentinhibition mechanisms.