Electrostatic and hydrophobic interactions during complex formation and electron transfer in the ferredoxin/ferredoxin: NADP{sup +} reductase system from Anabaena

Journal Article · Wed Jun 19 04:00:00 EDT 1996 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja953662a· OSTI ID:282953

Hurley, J K; Tollin, G ^[1]; Fillat, M F; Gomez-Moreno, C ^[2]

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1. Univ. of Arizona, Tucson, AZ (United States)
2. Universidad de Zaragoza (Spain)

Transient kinetics and protein-protein binding measurements over a wide range of ionic strength (I) have been used to characterize the interactions occurring during complex formation and electron transfer (et) between recombinant ferredoxin (Fd) and both native and recombinant ferredoxin: NADP{sup +} reductase (FNR) from the cyanobacterium Anabaena. Between I = 12 mM and I = 100 mM, the dissociation constant (K{sub d}) for the complex formed between oxidized Fd and oxidized native FNR increases from 4.5 to 8.1 {mu}M, whereas K{sub d} for the Fd complex with recombinant FNR increases from 0.3 to 3.3 {mu}M. For both pairs of proteins, the ionic strength dependence of k{sub obs} for the et reaction is biphasic. Electrostatic analysis of the kinetic data above I = 100 mM allows a prediction of the ionic strength dependence of the K{sub d} values, if electrostatic interactions are the only determinant of complex stability. The predicted dependence is dramatically larger than the observed one, indicating that hydrophobic interactions make an important contribution to complex stability. The differences in binding between native and recombinant FNR are ascribed to proteolytic cleavage at the N-terminus, which occurs during preparation of the native enzyme and which removes two positively charged residues, thereby decreasing the electrostatic interactions with Fd. 39 refs., 4 figs., 1 tab.

• OSTI ID: 282953
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 24 Vol. 118; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
55 BIOLOGY AND MEDICINE
BASIC STUDIES
BIOCHEMICAL REACTION KINETICS
DISSOCIATION
ELECTRON TRANSFER
ELECTROSTATICS
ENZYMES
FERREDOXIN
IRON COMPLEXES
PROTEINS