Study of the hydrophobic cavity of beta-cryptogein through laser-polarized xenon NMR spectroscopy.
The interaction of xenon with beta-cryptogein, a basic 10 kDa protein belonging to the elicitin family, has been studied by using dissolved thermal and laser-polarized gas in liquid-state NMR. 13C and 1H chemical-shift-mapping experiments were unfruitful, the proton lines only experienced a slight narrowing but no significant frequency variation when the xenon concentration was increased. Nevertheless magnetization transfer from hyperpolarized xenon to protons of the protein demonstrates an undoubted interaction and enables localization of the noble-gas-binding site. Due to the proton-proton cross-relaxation efficiency, however, this experiment is subjected to important spin-diffusion. An automatic procedure that takes spin-diffusion into account when assigning the protons that interact with xenon is then used. The binding site, as defined by 30 Xe--H interactions, is situated in the inner core of the protein. The protons that interact with xenon border the channel by which sterols are known to enter into the cavity. These results support the idea that xenon is a good probe for hydrophobic protein regions.
Berthault
Patrick
P
Laboratoire Structure et Dynamique par Résonance Magnétique, DSM/DRECAM/Service de Chimie Moléculaire, URA CEA/CNRS 331, CEA/Saclay, 91191 Gif sur Yvette, France. pberthault@cea.fr
Huber
Gaspard
G
Ha
Phuong Thu
PT
Dubois
Lionel
L
Desvaux
Hervé
H
Guittet
Eric
E
D020418:Algal Proteins / Q000737:chemistry*; D001665:Binding Sites; D002247:Carbon Isotopes; D018360:Crystallography, X-Ray; D005656:Fungal Proteins; D057927:Hydrophobic and Hydrophilic Interactions; D007834:Lasers; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards*; D008958:Models, Molecular; D011487:Protein Conformation; D011522:Protons; D012015:Reference Standards; D012680:Sensitivity and Specificity; D014978:Xenon / Q000737:chemistry* / Q000528:radiation effects
D020418:Algal Proteins; D002247:Carbon Isotopes; D005656:Fungal Proteins; D011522:Protons; C061032:cryptogein protein, Phytophthora cryptogea; D014978:Xenon