sup 14,15 N, sup 13 C, sup 57 Fe, and sup 1,2 H Q-band ENDOR study of Fe-S proteins with clusters that have endogenous sulfur ligands

Journal Article · Tue Feb 25 04:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00122a026· OSTI ID:5640039

Houseman, A L.P.; Fan, Chaoliang; Werst, M M; Hoffman, B M ^[1]; Oh, Byungha; Markley, J L ^[2]; Kennedy, M C; Beinert, H ^[3]

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1. Northwestern Univ., Evanston, IL (United States)
2. Univ. of Wisconsin, Madison (United States)
3. Medical College of Wisconsin, Milwaukee (United States)

The benefits of performing ENDOR experiments at higher microwave frequency are demonstrated in a Q-band (35 GHz) ENDOR investigation of a number of proteins with (nFe-mS) clusters, n = 2,3,4. Each protein displays several resonances in the frequency range of 0-20 MHz. In all instances, features are seen near {nu} {approx} 13 and 8 MHz that can be assigned, respectively, to distant ENDOR from {sup 13}C in natural-abundance (1.1%) and from {sup 14}N. In addition, a number of proteins show local {sup 13}C ENDOR signals with resolved hyperfine interactions; these are assigned to the {beta} carbons of cysteines bound to the cluster. Quadrupole coupling constants are derived for both local and distant {sup 14}N signals. The interpretation of the data is supported by studies on {sup 15}N- and {sup 13}C-enriched ferredoxin (Fd) from Anabaena 7120, where the {sup 15}N signals can be clearly correlated with the corresponding {sup 14}N signals and where the {sup 13}C signals are strongly enhanced. Thus, the observation of {sup 14}N {Delta}m{sub I} = {plus minus} 2 signals at Q-band provides a new technique for examining weak interactions with a cluster. Six proteins show an additional pattern near {nu} {approx} 18 MHz that arises from {sup 57}Fe in natural abundance (2.2%) with A({sup 57}Fe) {approx} 36 MHz, which opens the possibility of studying proteins for which enrichment is impractical. Q-band ENDOR studies also have been carried out on four {sup 2}H-exchanged Fe-S proteins, and ENDOR detects exchangeable protons in each. The importance of these findings for the interpretation of X- and Q-band ENDOR at low radiofrequencies is discussed.

• OSTI ID: 5640039
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 31:7; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ALGAE
BARYONS
CARBON 13
CARBON ISOTOPES
DEUTERIUM COMPOUNDS
ELEMENTARY PARTICLES
ENDOR
EVEN-ODD NUCLEI
FERMIONS
FERREDOXIN
FREQUENCY RANGE
HADRONS
HYDROGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
IRON 57
IRON ISOTOPES
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
METALLOPROTEINS
MICROORGANISMS
MOLECULAR STRUCTURE
NITROGEN 14
NITROGEN 15
NITROGEN ISOTOPES
NUCLEI
NUCLEONS
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PLANTS
PROTEINS
PROTONS
RESONANCE
STABLE ISOTOPES
UNICELLULAR ALGAE