Crystal structure of brefeldin A esterase, a bacterial homolog of the mammalian hormone-sensitive lipase

Brefeldin A esterase (BFAE), a detoxifying enzyme isolated from Bacillus su btilis, hydrolyzes and inactivates BFA, a potent fungal inhibitor of intrac ellular vesicle-dependent secretory transport and poliovirus RNA replicatio n. We have solved the crystal structure of BFAE and we discovered that the previously reported amino acid sequence was in serious error due to frame s hifts in the cDNA sequence. The correct sequence, inferred from the experim entally phased electron density map, revealed that BFAE is a homolog of the mammalian hormone sensitive lipase (HSL). It is a canonical alpha/beta hyd rolase with two insertions forming the substrate binding pocket. The enzyme contains a lipase-like catalytic triad, Ser 202, Asp 308 and His 338, cons istent with mutational studies that implicate the homologous Ser 424, Asp 6 93 and His 723 in the catalytic triad in human HSL.