Hydrogen bonding of sulfur ligands in blue copper and iron-sulfur proteins: detection by resonance raman spectroscopy
The resonance Raman spectrum of the blue copper protein azurin from Alcaligenes denitrificans exhibits nine vibrational modes between 330 and 460 cm/sup -1/, seven of which shift 0.4-3.0 cm/sup -1/ to lower energy after incubation of the protein in D/sub 2/O. These deuterium-dependent shifts have been previously ascribed to exchangeable protons on imidazole ligands or to exchangeable protons on amide groups which are hydrogen bonded to the cysteine thiolate ligands (a feature common to all blue copper proteins of known structure). In order to distinguish between these two possibilities, a systematic investigation of Fe/sub 2/S/sub 2/(Cys)/sub 4/-containing proteins was undertaken. Extensive hydrogen bonding between sulfur ligands and the polypeptide backbone had been observed in the crystal structure of ferredoxin from Spirulina platensis. The resonance Raman spectrum of this protein is typical of a chloroplast-type ferredoxin and exhibits deuterium-dependent shifts of -0.3 to -0.5 cm/sup -1/ in the Fe-S modes at 283, 367, and 394 cm/sup -1/ and -0.6 to -0.8 cm/sup -1/ in the Fe-S modes at 328 and 341 cm/sup -1/. Considerably greater deuterium sensitivity is observed in the Raman spectra of spinach ferredoxin and bovine adrenodoxin, particularly for the symmetric stretching vibration of the Fe/sub 2/S/sub 2/ moiety at approx. 390 cm/sup -1/. This feature decreases of 9.8 and 1.1 cm/sup -1/, respectively, for the two oxidized proteins in D/sub 2/O and by 1.8 cm/sup -1/ for reduced adrenodoxin in D/sub 2/O. These results suggest that the bridging sulfido groups may be more extensively hydrogen bonded in spinach ferredoxin and adrenodoxin than in S. platensis ferredoxin, with a further increase in hydrogen-bond strength in the reduced form of adrenodoxin.
- Research Organization:
- Oregon Graduate Center, Beaverton
- OSTI ID:
- 5444471
- Journal Information:
- Biochemistry; (United States), Vol. 26:25
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
METALLOPROTEINS
RAMAN SPECTROSCOPY
BACTERIA
CHEMICAL BONDS
COPPER COMPLEXES
FERREDOXIN
HEAVY WATER
IRON COMPLEXES
LIGANDS
RAMAN SPECTRA
SPINACH
COMPLEXES
FOOD
HYDROGEN COMPOUNDS
LASER SPECTROSCOPY
MICROORGANISMS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PLANTS
PROTEINS
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
VEGETABLES
WATER
550601* - Medicine- Unsealed Radionuclides in Diagnostics