Structure-function relationships in human cytochrome c: The role of tyrosine 67.

Structure-function relationships in human cytochrome c: The role of tyrosine 67.
J Inorg Biochem. 2015 Nov 12;155:56-66
Authors: Tognaccini L, Ciaccio C, D'Oria V, Cervelli M, Howes BD, Coletta M, Mariottini P, Smulevich G, Fiorucci L
Abstract
Spectroscopic and functional properties of human cytochrome c and its Tyr67 residue mutants (i.e., Tyr67His and Tyr67Arg) have been investigated. In the case of the Tyr67His mutant, we have observed only a very limited structural alteration of the heme pocket and of the Ω-loop involving, among others, the residue Met80 and its bond with the heme iron. Conversely, in the Tyr67Arg mutant the Fe-Met80 bond is cleaved; consequently, a much more extensive structural alteration of the Ω-loop can be envisaged. The structural, and thus the functional modifications, of the Tyr67Arg mutant are present in both the ferric [Fe(III)] and the ferrous [Fe(II)] forms, indicating that the structural changes are independent of the heme iron oxidation state, depending instead on the type of substituting residue. Furthermore, a significant peroxidase activity is evident for the Tyr67Arg mutant, highlighting the role of Arg as a basic, positively charged residue at pH7.0, located in the heme distal pocket, which may act as an acid to cleave the O-O bond in H2O2. As a whole, our results indicate that a delicate equilibrium is associated with the spatial arrangement of the Ω-loop. Clearly, Arg, but not His, is able...

Source: Journal of Inorganic Biochemistry - November 12, 2015 Category: Biochemistry Authors: Tognaccini L, Ciaccio C, D'Oria V, Cervelli M, Howes BD, Coletta M, Mariottini P, Smulevich G, Fiorucci L Tags: J Inorg Biochem Source Type: research