Phosphorus-31 NMR Study of Pyridoxal 5’-Phosphate Binding to Escherichia Coli Tryptophan Synthase Modified by Limited Proteolysis

Summary

The β₂ subunit of α₂β₂ tryptophan synthase from Escherichia coli has been proteolyzed by limited treatment with protease from Staphylococcus aureus, V8. Interaction of this derivative (nicked β₂) with pyridoxal-P has been investigated using ³¹P nuclear magnetic resonance (NMR). The phosphate signal of pyridoxal-P shows a linewidth significantly smaller than expected for a rigidly bound cofactor molecule. Upon addition of the corresponding a subunit further line narrowing is observed indicating that the nicked β₂ protein is still capable to form a native-like α₂β₂ complex. These results are compared with data for both the native β₂ subunit and the α₂ holo β₂ complex.