title: Effects of NAD+ binding on the luminescence of tryptophans 84 and 310 of glyceraldehyde-3-phosphate dehydrogenase from Bacillus stearothermophilus.
abstract: The individual fluorescence and phosphorescence properties of W84 and W310 in Bacillus stearothermophilus glyceraldehyde-3-phosphate dehydrogenase were identified through the construction of a single tryptophan mutant (W84F) and by comparison of the emission between mutant and wild-type enzymes. The results show that the luminescence of W310 is red-shifted and substantially quenched relative to that of W84. It displays an average subnanosecond fluorescence lifetime (tau F) and a very short, 50 microseconds, room-temperature phosphorescence (RTP) lifetime (tau P). The perturbation of W310 luminescence is believed to arise from a stacking interaction with Y283. In contrast, W84 exhibits a fluorescence lifetime tau F of several nanoseconds and a long-lived phosphorescence lifetime tau P, typical of buried, unperturbed TrP residues. NAD+ binding to the tetrameric enzyme causes a 55% reduction of W310 fluorescence intensity together with a nearly complete quenching of its low-temperature phosphorescence. W84, which is located far from the nicotinamide moiety of NAD+, is much less affected by the binding of the coenzyme; the reduction in fluorescence intensity is 35%, and its phosphorescence intensity is unchanged. Another consequence of NAD+ binding is a significant decrease of the RTP lifetime tau P of W84, manifesting thereby a conformational change in the region of the coenzyme-binding domain. However, no change is observed in the RTP lifetime tau P of W310 located in the catalytic domain. These findings and those obtained at partial coenzyme saturation support the conclusions derived from high-resolution crystallographic structures [Skarzynski, T., & Wonacott, A. J., (1988) J. Mol. Biol. 203, 1097-1118] that the NAD(+)-induced conformational change is sequential and that subtle rearrangement in the structure of unligated subunits might be responsible for the negative cooperative behavior of NAD+ binding.
authors.affiliation: Istituto di Biofisica-CNR, Pisa, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Gabellieri
authors.forename: S
authors.initials: S
authors.lastname: Rahuel-Clermont
authors.forename: G
authors.initials: G
authors.lastname: Branlant
authors.forename: G B
authors.initials: GB
authors.lastname: Strambini
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D005453:Fluorescence; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008163:Luminescent Measurements; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009243:NAD / Q000031:analogs & derivatives / Q000378:metabolism*; D011487:Protein Conformation; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009243:NAD; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D014364:Tryptophan; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases