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The pH dependent spectral properties of Clostridium pasteurianum 2[Fe 4 S 4 ] ferredoxin
Author(s) -
Calzolai Luigi,
Messori Luigi,
Monnanni Roberto
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00728-4
Subject(s) - ferredoxin , deprotonation , chemistry , cluster (spacecraft) , iron–sulfur cluster , cysteine , chemical shift , crystallography , absorption (acoustics) , clostridium , stereochemistry , analytical chemistry (journal) , biochemistry , organic chemistry , physics , bacteria , ion , enzyme , biology , computer science , programming language , acoustics , genetics
The recently assigned 1 H NMR hyperfine signals of Clostridium pasteurianum ferredoxin were investigated over the pH range 8–12 to monitor possible pH‐dependent conformational changes of the protein. For very high pH values minor perturbations were detected in the chemical shifts of three signals assigned to β‐CH 2 , cysteine protons of cluster II, while cluster I was not affected at all. These chemical shift variations, which can be fitted to a single p K a ≈ 10.9, are interpreted as an effect of deprotonation of the phenolic group of Tyr‐2, located reasonably close to cluster II. This hypothesis has been supported by means of other techniques such as CD and absorption spectroscopy that, on turn, are able to reveal minor pH‐dependent spectral variations at high pH. Finally a UV difference experiment has provided further evidence for deprotonation of the phenolic group of Tyr‐2. The possible influence of deprotonation of Tyr‐2 on the redox properties of cluster II is discussed.