ABSTRACT
The anaerobically inducible L-serine dehydratase, TdcG, from Escherichia coli was characterized. Based on UV-visible spectroscopy, iron and labile sulfide analyses, the homodimeric enzyme is proposed to have two oxygen-labile [4Fe-4S]2+ clusters. Anaerobically isolated dimeric TdcG had a kcat of 544 s(-1) and an apparent KM for L-serine of 4.8 mM. L-threonine did not act as a substrate for the enzyme. Exposure of the active enzyme to air resulted in disappearance of the broad absorption band at 400-420 nm, indicating a loss of the [4Fe-4S]2+ cluster. A concomitant loss of dehydratase activity was demonstrated, indicating that integrity of the [4Fe-4S]2+ cluster is essential for enzyme activity.
Subject(s)
Escherichia coli/enzymology , Iron-Sulfur Proteins/metabolism , L-Serine Dehydratase/metabolism , Dimerization , Escherichia coli Proteins/metabolism , Kinetics , Spectrophotometry , Sulfides/metabolismABSTRACT
Crystals of the hypothetical protein TdcF (subunit MW = 14 007) from Escherichia coli were grown by vapour diffusion. The protein crystallizes in space group P2(1)2(1)2, with unit-cell parameters a = 72.67, b = 86.22, c = 62.62 A. Native data to a resolution of 2.35 A were collected from a single crystal at 100 K on a rotating-anode X-ray generator. Preliminary analysis of these data indicated that the asymmetric unit corresponded to a trimer, which was supported by a convincing molecular-replacement solution using the YjgF trimer as the probe structure.
