Escherichia coli L-serine deaminase requires a [4Fe-4S] cluster in catalysis.

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Cicchillo RM, Baker MA, Schnitzer EJ, Newman EB, Krebs C, Booker SJ

Escherichia coli L-serine deaminase requires a [4Fe-4S] cluster in catalysis.

J Biol Chem. 2004 Jul 30;279(31):32418-25. Epub 2004 May 19.

PubMed ID

15155761 [ View in PubMed

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Abstract

L-Serine deaminases catalyze the deamination of L-serine, producing pyruvate and ammonia. Two families of these proteins have been described and are delineated by the cofactor that each employs in catalysis. These are the pyridoxal 5'-phosphate-dependent deaminases and the deaminases that are activated in vitro by iron and dithiothreitol. In contrast to the enzymes that employ pyridoxal 5'-phosphate, detailed physical and mechanistic characterization of the iron-dependent deaminases is limited, primarily because of their extreme instability. We report here the characterization of L-serine deaminase from Escherichia coli, which is the product of the sdaA gene. When purified anaerobically, the isolated protein contains 1.86 +/- 0.46 eq of iron and 0.670 +/- 0.019 eq of sulfide per polypeptide and displays a UV-visible spectrum that is consistent with a [4Fe-4S] cluster. Reconstitution of the protein with iron and sulfide generates considerably more of the cluster, and treatment of the reconstituted protein with dithionite gives rise to an axial EPR spectrum, displaying g axially = 2.03 and g radially = 1.93. Mossbauer spectra of the (57)Fe-reconstituted protein reveal that the majority of the iron is in the form of [4Fe-4S](2+) clusters, as evidenced by the typical Mossbauer parameters-isomer shift, delta = 0.47 mm/s, quadrupole splitting of Delta E(Q) = 1.14 mm/s, and a diamagnetic (S = 0) ground state. Treatment of the dithionite-reduced protein with L-serine results in a slight broadening of the feature at g = 2.03 in the EPR spectrum of the protein, and a dramatic loss in signal intensity, suggesting that the amino acid interacts directly with the cluster.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Pyridoxal phosphate	L-serine dehydratase/L-threonine deaminase	Protein	Humans	Unknown	Cofactor	Details