113CD-1H spin-spin couplings in homonuclear 1H correlated spectroscopy of metallothionein. Identification of the cysteine 1H spin systems.
Heteronuclear spin-spin couplings between 113Cd and C beta protons of the metal-bound cysteines were observed in phase-sensitive, double-quantum filtered, homonuclear two-dimensional correlated (COSY) 1H NMR spectra of 113Cd-metallothionein-2 from rabbit liver. Comparison of 113Cd- and 112Cd-metallothionein-2 spectra revealed that 19 1H spin systems show heteronuclear couplings to at least one 113Cd and were thus identified as 19 of the 20 cysteines in this protein. From a detailed analysis of the manifestations of heteronuclear couplings in the homonuclear 1H COSY spectra, two cysteines could be identified as 'bridging cysteines', with spin-spin couplings to two different 113Cd nuclei. The observed 113Cd-1H coupling constants vary between less than or equal to 5 Hz and 80 Hz.
D000818:Animals; D002104:Cadmium; D055598:Chemical Phenomena; D002621:Chemistry; D003545:Cysteine / Q000032:analysis*; D007554:Isotopes; D008099:Liver / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008668:Metallothionein; D011522:Protons; D011817:Rabbits; D013057:Spectrum Analysis / Q000379:methods
D007554:Isotopes; D011522:Protons; D002104:Cadmium; D008668:Metallothionein; D003545:Cysteine