Suicide inactivation of MauG during reaction with O(2) or H(2)O(2) in the absence of its natural protein substrate.
MauG is a diheme protein that catalyzes the six-electron oxidation of a biosynthetic precursor protein of methylamine dehydrogenase (PreMADH) with partially synthesized tryptophan tryptophylquinone (TTQ) to yield the mature protein with the functional protein-derived TTQ cofactor. The biosynthetic reaction proceeds via a relatively stable high valent bis-Fe(IV) intermediate. Oxidizing equivalents ([O]) for this reaction may be provided by either O(2) plus electrons from an external donor or H(2)O(2). The presence or absence of PreMADH has no influence on the reactivity of MauG with [O]; however, it is demonstrated that MauG is inactivated when supplied with [O] in the absence of PreMADH. The mechanism of inactivation appears to differ depending on the source of [O]. Repeated reaction of diferrous MauG with O(2) leads to loss of activity but not inactivation of heme, as judged by absorption spectroscopy and pyridine hemochrome assay. Repeated reaction of diferric MauG with H(2)O(2) leads to loss of activity and inactivation of heme, as well as some covalent cross-linking of MauG molecules. None of these deleterious effects with either source of [O] are observed when PreMADH is present to react with MauG. The radical scavenger hydroxyurea and small molecule mimics of the monohydroxylated Trp residue of PreMADH also reacted with bis-Fe(IV) MauG and afforded protection against inactivation. These results demonstrate that while O(2) and H(2)O(2) readily react with MauG in the absence of PreMADH, the presence of this substrate is necessary to prevent suicide inactivation of MauG after formation of the bis-Fe(IV) intermediate.
Shin
Sooim
S
Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi 39216, USA.
Lee
Sheeyong
S
Davidson
Victor L
VL
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000737:chemistry* / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D010084:Oxidation-Reduction; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; C404449:heme protein, bacteria; D014364:Tryptophan; D006861:Hydrogen Peroxide; C021567:methylamine dehydrogenase; D000587:Oxidoreductases Acting on CH-NH Group Donors; D010100:Oxygen