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High affinity copper binding by stefin B (cystatin B) and its role in the inhibition of amyloid fibrillation
Author(s) -
Žerovnik Eva,
Škerget Katja,
TušekŽnidarič Magda,
Loeschner Corina,
Brazier Marcus W.,
Brown David R.
Publication year - 2006
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2006.05426.x
Subject(s) - isothermal titration calorimetry , chemistry , copper , cystatin , gene isoform , amyloid (mycology) , biochemistry , protease , plasma protein binding , biophysics , cystatin c , biology , enzyme , inorganic chemistry , organic chemistry , renal function , gene
We show that human stefin B, a protease inhibitor from the family of cystatins, is a copper binding protein, unlike stefin A. We have used isothermal titration calorimetry to directly monitor the binding event at pH 7 and pH 5. At pH 7 stefin B shows a picomolar affinity for copper but at pH 5 the affinity is in the nanomolar range. There is no difference in the affinity of copper between the wildtype stefin B (E31 isoform) and a variant (Y31 isoform), whereas the mutant (P79S), which is tetrameric, does not bind copper. The conformation of stefin B remains unaltered by copper binding. It is known that below pH 5 stefin B undergoes a conformational change and amyloid fibril formation. We show that copper binding inhibits the amyloid fibril formation and, to a lesser degree, the initial aggregation. Similarities to and differences from other copper binding amyloidogenic proteins are discussed.