Structural insights into bacterial resistance to cerulenin

TRAJTENBERG F; ALTABE, S; LARRIEUX N; FICARRA F; DE MENDOZA, D; BUSCHIAZZO, A; SCHUJMAN, GE

FEBS JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 281 p. 2324 - 2338

1742-464X

Cerulenin is a fungal toxin that inhibits both eukaryotic and prokaryoticketoacyl-acyl carrier protein synthases or condensing enzymes. It has beenused experimentally to treat cancer and obesity, and is a potent inhibitorof bacterial growth. Understanding the molecular mechanisms of resistanceto cerulenin and similar compounds is thus highly relevant for humanhealth. We have previously described a Bacillus subtilis cerulenin-resistantstrain, expressing a point-mutated condensing enzyme FabF (FabF[I108F])(i.e. FabF with isoleucine 108 substituted by phenylalanine). We nowreport the crystal structures of wild-type FabF from B. subtilis, both aloneand in complex with cerulenin, as well as of the FabF[I108F] mutant protein.The three-dimensional structure of FabF[I108F] constitutes the firstatomic model of a condensing enzyme that remains active in the presenceof the inhibitor. Soaking the mycotoxin into preformed wild-type FabFcrystals allowed for noncovalent binding into its specific pocket within theFabF core. Interestingly, only co-crystallization experiments allowed us totrap the covalent complex. Our structure shows that the covalent bondbetween Cys163 and cerulenin, in contrast to that previously proposed,implicates carbon C3 of the inhibitor. The similarities between Escherichiacoli and B. subtilis FabF structures did not explain the reported inabilityof ecFabF[I108F] (i.e. FabF from Escherichia coli with isoleucine 108substituted by phenylalanine) to elongate medium and long-chain acyl-ACPs. We now demonstrate that the E. coli modified enzyme efficientlycatalyzes the synthesis of medium and long-chain ketoacyl-ACPs. We alsocharacterized another cerulenin-insensitive form of FabF, conferring a differentphenotype in B. subtilis. The structural, biochemical and physiologicaldata presented, shed light on the mechanisms of FabF catalysis andresistance to cerulenin.