Malonyl-ACP, a putative signal for the global fatty acid regulator FapR of Bacillus subtilis

MARIANO MARTINEZ,; ME ZABALLA; SCHAEFFER, F; ALZARI, P; GUSTAVO E. SCHUJMAN; VILA, A; DIEGO DE MENDOZA

Carlos Paz

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigadores en Bioquímica (SAIB); 2008

SAIB

Fatty acid biosynthesis is essential for bacterial growth, and its homeostasis is critical for survival. In many Gram positive bacteria, this accurate regulation is established trough the action of the global transcriptional repressor FapR. We have shown that the signal sensed by FapR is malonyl-CoA, a key precursor of fatty acid biosynthesis. Another key component of this biosynthetic pathway is the acyl carrier protein (ACP), which binds all the acyl intermediates and presents them to the different enzymes of this metabolic route. The structural characterization of the malonyl- CoA–FapR complex indicated that all the atoms of malonyl-CoA involved in the interaction are also present in malonyl-ACP, which contains a phosphopantetheine prosthetic group. The objective of this work was to test in vitro if malonyl-ACP is able to interact with FapR, and to act as an effector of this regulator. To characterize the nature of the interaction, we performed isothermal titration microcalorimetry of FapR with malonyl-ACP. To identify the aminoacidic residues of malonyl-ACP involved in the interaction we carried out NMR titrations of 15N-malonyl-ACP with FapR. Finally, we confirmed that malonyl-ACP releases FapR from its operator sequences by in vitro transcription. Our results indicate that malonyl-ACP is also a signal for FapR regulation.