13C and 15N NMR studies on the interaction between 6,7-dimethyl-8-ribityllumazine and lumazine protein.
The interaction between the prosthetic group 6,7-dimethyl-8-(1'-D-ribityl)lumazine and the lumazine apoproteins from two marine bioluminescent bacteria, one from a relatively thermophilic species, Photobacterium leiognathi, and the other from a psychrophilic species, Photobacterium phosphoreum, was studied by 13C and 15N NMR using various selectively enriched derivatives. It is shown that the electron distribution in the protein-bound 6,7-dimethyl-8-ribityllumazine differs from that of free 6,7-dimethyl-8-ribityllumazine in buffer. The 13C and 15N chemical shifts indicate that the protein-bound 6,7-dimethyl-8-ribityllumazine is embedded in a polar environment and that the ring system is strongly polarized. It is concluded that the two carbonyl groups play an important role in the polarization of the molecule. The N(3)-H group is not accessible to bulk solvent. The N(8) atom is sp2 hybridized and has delta+ character. Nuclear Overhauser effect studies indicate that the 6,7-dimethyl-8-ribityllumazine ring is rigidly bound with no internal mobility. The NMR results indicate that the interaction between the ring system and the two apoproteins is almost the same.
Vervoort
J
J
Department of Biochemistry, Agricultural University, HA Wageningen, The Netherlands.
O'Kane
D J
DJ
Müller
F
F
Bacher
A
A
Strobl
G
G
Lee
J
J
D001426:Bacterial Proteins / Q000378:metabolism*; D002247:Carbon Isotopes; D002352:Carrier Proteins / Q000378:metabolism*; D008163:Luminescent Measurements; D008164:Luminescent Proteins; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009153:Mutagens; D009587:Nitrogen Isotopes; D010776:Photobacterium / Q000378:metabolism*; D011485:Protein Binding; D011621:Pteridines / Q000378:metabolism*; D013045:Species Specificity
D001426:Bacterial Proteins; D002247:Carbon Isotopes; D002352:Carrier Proteins; D008164:Luminescent Proteins; D009153:Mutagens; D009587:Nitrogen Isotopes; D011621:Pteridines; C026648:lumazine protein, Photobacterium; C001061:6,7-dimethyl-8-ribityllumazine