Structural and Biochemical Investigations of the [4Fe-4S] Cluster-Containing Fumarate Hydratase fromLeishmania major.Feliciano, P.R., Drennan, C.L.
(2019) Biochemistry 58: 5011-5021
- PubMed: 31743022
- DOI: 10.1021/acs.biochem.9b00923
- Primary Citation of Related Structures:
- PubMed Abstract:
Class I fumarate hydratases (FHs) are central metabolic enzymes that use a [4Fe-4S] cluster to catalyze the reversible conversion of fumarate to <i>S </i>-malate. The parasite <i>Leishmania major </i>, which is responsible for leishmaniasis, expres ...
Class I fumarate hydratases (FHs) are central metabolic enzymes that use a [4Fe-4S] cluster to catalyze the reversible conversion of fumarate to S -malate. The parasite Leishmania major , which is responsible for leishmaniasis, expresses two class I FH isoforms: mitochondrial LmFH-1 and cytosolic LmFH-2. In this study, we present kinetic characterizations of both LmFH isoforms, present 13 crystal structures of LmFH-2 variants, and employ site-directed mutagenesis to investigate the enzyme's mechanism. Our kinetic data confirm that both LmFH-1 and LmFH-2 are susceptible to oxygen-dependent inhibition, with data from crystallography and electron paramagnetic resonance spectroscopy showing that oxygen exposure converts an active [4Fe-4S] cluster to an inactive [3Fe-4S] cluster. Our anaerobically conducted kinetic studies reveal a preference for fumarate over S -malate. Our data further reveal that single alanine substitutions of T467, R421, R471, D135, and H334 decrease k cat values 9-16000-fold without substantially affecting K m values, suggesting that these residues function in catalytic roles. Crystal structures of LmFH-2 variants are consistent with this idea, showing similar bidentate binding to the unique iron of the [4Fe-4S] cluster for substrate S -malate as observed in wild type FH. We further present LmFH-2 structures with substrate fumarate and weak inhibitors succinate and malonate bound in the active site and the first structure of an LmFH that is substrate-free and inhibitor-free, the latter showing increased mobility in the C-terminal domain. Collectively, these data provide insight into the molecular basis for the reaction catalyzed by LmFHs, enzymes that are potential drug targets against leishmaniasis.
Howard Hughes Medical Institute , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.,Department of Biology , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.,Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.