Cytochrome rC552, formed during expression of the truncated, Thermus thermophilus cytochrome c552 gene in the cytoplasm of Escherichia coli, reacts spontaneously to form protein-bound 2-formyl-4-vinyl (Spirographis) heme.
Expression of the truncated (lacking an N-terminal signal sequence) structural gene of Thermus thermophilus cytochrome c(552) in the cytoplasm of Escherichia coli yields both dimeric (rC(557)) and monomeric (rC(552)) cytochrome c-like proteins [Keightley, J. A., et al. (1998) J. Biol. Chem. 273, 12006-12016], which form spontaneously without the involvement of cytochrome c maturation factors. Cytochrome rC(557) is comprised of a dimer and has been structurally characterized [McRee, D., et al. (2001) J. Biol. Chem. 276, 6537-6544]. Unexpectedly, the monomeric rC(552) transforms spontaneously to a cytochrome-like chromophore having, in its reduced state, the Q(oo) transition (alpha-band) at 572 nm (therefore called p572). The X-ray crystallographic structure of rC(552), at 1.41 A resolution, shows that the 2-vinyl group of heme ring I is converted to a [heme-CO-CH(2)-S-CH(2)-C(alpha)] conjugate with cysteine 11. Electron density maps obtained from isomorphous crystals of p572 at 1.61 A resolution reveal that the 2-vinyl group has been oxidized to a formyl group. This explains the lower energy of the Q(oo)() transition, the presence of a new, high-frequency band in the resonance Raman spectra at 1666 cm(-1) for oxidized and at 1646 cm(-1) for reduced samples, and the greatly altered, paramagnetically shifted (1)H NMR spectrum observed for this species. The overall process defines a novel mechanism for oxidation of the 2-vinyl group to a 2-formyl group and adds to the surprising array of chemical reactions that occur in the interaction of heme with the CXXCH sequence motif in apocytochromes c.
Fee
James A
JA
Department of Biology, University of California at San Diego, La Jolla, California 92093, USA. jafee@scripps.edu
Todaro
Thomas R
TR
Luna
Eugene
E
Sanders
Donita
D
Hunsicker-Wang
Laura M
LM
Patel
Kirti M
KM
Bren
Kara L
KL
Gomez-Moran
Ester
E
Hill
Michael G
MG
Ai
Jingyuan
J
Loehr
Thomas M
TM
Oertling
W Anthony
WA
Williams
Pamela A
PA
Stout
C David
CD
McRee
Duncan
D
Pastuszyn
Andrzej
A
D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D003573:Cytochrome b Group / Q000737:chemistry / Q000378:metabolism; D003574:Cytochrome c Group / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D006418:Heme / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion / Q000235:genetics; D013057:Spectrum Analysis; D013059:Spectrum Analysis, Raman; D016963:Thermus thermophilus / Q000201:enzymology* / Q000235:genetics*
C492916:2-formyl-4-vinylheme; D003573:Cytochrome b Group; D003574:Cytochrome c Group; D006418:Heme; C022302:cytochrome C-552; C058557:cytochrome ba3; D003576:Electron Transport Complex IV