Experimental evidence for a link among cupredoxins: Red, blue, and purple copper transformations in nitrous oxide reductase

Masha G. Savelieff, Tiffany D. Wilson, Youssef Elias, Mark J. Nilges, Dewain K. Garner, Yi Lu

Research output: Contribution to journalArticlepeer-review


The cupredoxin fold is an important motif in numerous proteins that are central to several critical cellular processes ranging from aerobic and anaerobic respiration to catalysis and iron homeostasis. Three types of copper sites have been found to date within cupredoxin folds: blue type 1 (T1) copper, red type 2 (T2) copper, and purple CuA. Although as much as 90% sequence difference has been observed among some members of this superfamily of proteins that span several kingdoms, sequence alignment and phylogenic trees strongly suggest an evolutionary link and common ancestry. However, experimental evidence for such a link has been lacking. We report herein the observation of pH-dependent transformation between blue T1 copper, red T2 copper, and the native purple CuA centers of nitrous oxide reductase (N 2OR) from Paracoccus denitrificans. The blue and red copper centers form initially before they are transformed into purple CuA center. This transformation process is pH-dependent, with lower pH resulting in fewer trapped T1 and T2 coppers and faster transition to purple CuA. These observations suggest that the purple CuA site contains the essential elements of T1 and T2 copper centers and that the CuA center is preferentially formed at low pH. Therefore, this work provides an underlying link between the various cupredoxin copper sites and possible experimental evidence in vitro for the evolutionary relationship between the cupredoxin proteins. The findings also lend physiological relevance to cupredoxin site biosynthesis.

Original languageEnglish (US)
Pages (from-to)7919-7924
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number23
StatePublished - Jun 10 2008


  • Blue type 1 copper
  • Folding
  • Kinetics
  • Purple copper Cu
  • Red type 2 copper

ASJC Scopus subject areas

  • Genetics
  • General


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