The environments of Trp-248 and Trp-330 in tryptophan indole-lyase from Escherichia coli.
The two tryptophan residues, Trp-248 and Trp-330, in tryptophan indole-lyase (tryptophanase) from E. coli have been separately mutated to phenylalanine using site-directed mutagenesis. Both single tryptophan mutant enzymes have full catalytic activity, but exhibit different fluorescence and near-UV circular dichroism spectra. These results indicate that Trp-330 is more deeply buried than is Trp-248, and is in a more asymmetric environment. Neither residue reacts with N-bromosuccinimide (NBS), although tryptophan indole-lyase is inactivated by NBS. These results demonstrate that the tryptophan residues in tryptophan indole-lyase are not catalytically essential.
Department of Chemistry, School of Chemical Sciences, University of Georgia, Athens 30602.
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Phillips
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Gollnick
D001665:Binding Sites; D001974:Bromosuccinimide; D002942:Circular Dichroism; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000201:enzymology*; D008190:Lyases / Q000378:metabolism*; D011487:Protein Conformation; D011732:Pyridoxal Phosphate / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan; D014368:Tryptophanase / Q000235:genetics / Q000378:metabolism*
D011732:Pyridoxal Phosphate; D014364:Tryptophan; D008190:Lyases; D014368:Tryptophanase; D001974:Bromosuccinimide