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. Author manuscript; available in PMC: 2008 Sep 12.
Published in final edited form as: Biochemistry. 2006 Dec 19;45(51):15405–15410. doi: 10.1021/bi062026u

Figure 7.

Figure 7

A novel crosslinked cofactor is present in all three heme-copper oxygen reductase families. (A) The active-site tyrosine forming the cofactor originates from helix VI in the A- and B-type oxygen reductases, while in the C-type oxygen reductases it originates from helix VII. This is the first example of the evolutionary migration of a post-translationally modified active-site residue. (B) The crosslink is formed between a histidine and tyrosine within helix VI in the A- and B-type oxygen reductases. In the C-type oxygen reductases the crosslink is formed between a histidine in helix VI and a tyrosine in helix VII, covalently coupling the helices together. This figure was generated using VMD software (45).