Interaction between the formyl group of heme a and arginine 54 in cytochrome aa(3) from Paracoccus denitrificans

The optical spectrum of heme a is red-shifted in aa(3)-type cytochrome c ox idases compared to isolated low-spin heme A model compounds. Early spectros copic studies indicated that this may be due to hydrogen-bonding of the for myl group of heme a to an amino acid in the close vicinity. Here we show th at most of the optical spectral shift of native heme a is due to a hydrogen -bonding interaction between the formyl group and arginine-54 in subunit I of cytochrome aa(3) from Paracoccus denitrificans, and that a smaller part is due to an electrostatic interaction between the D ring propionate of hem e a and arginine-474. (C) 2000 Elsevier Science B.V. All rights reserved.