Disulfide bond formation involves a quinhydrone-type charge–transfer complex
AUTOR(ES)
Regeimbal, James
FONTE
National Academy of Sciences
RESUMO
The chemistry of disulfide exchange in biological systems is well studied. However, the detailed mechanism of how oxidizing equivalents are derived to form disulfide bonds in proteins is not clear. In prokaryotic organisms, it is known that DsbB delivers oxidizing equivalents through DsbA to secreted proteins. DsbB becomes reoxidized by reducing quinones that are part of the membrane-bound electron-transfer chains. It is this quinone reductase activity that links disulfide bond formation to the electron transport system. We show here that purified DsbB contains the spectral signal of a quinhydrone, a charge–transfer complex consisting of a hydroquinone and a quinone in a stacked configuration. We conclude that disulfide bond formation involves a stacked hydroquinone–benzoquinone pair that can be trapped on DsbB as a quinhydrone charge–transfer complex. Quinhydrones are known to be redox-active and are commonly used as redox standards, but, to our knowledge, have never before been directly observed in biological systems. We also show kinetically that this quinhydrone-type charge–transfer complex undergoes redox reactions consistent with its being an intermediate in the reaction mechanism of DsbB. We propose a simple model for the action of DsbB where a quinhydrone-like complex plays a crucial role as a reaction intermediate.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=283498Documentos Relacionados
- Polarons and excitons in charge-transfer systems
- Role of charge-transfer states in bacterial photosynthesis
- QUANTUM CHEMICAL STUDIES OF CHARGE-TRANSFER COMPLEXES OF INDOLES*
- Tunneling in Chromatium chromatophores: Detection of a Hopfield charge-transfer band
- Crystal structure of a complex between lumiflavin and 2,6-diamino-9-ethylpurine: a flavin adenine dinucleotide model exhibiting charge-transfer interactions.
