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Qo Site of the Bc1 Complex ; Unlocking the Gate of the Electron Transport Chain

出版	University of Illinois at Urbana-Champaign, 2015
URL	http://books.google.com.hk/books?id=w6UojwEACAAJ&hl=&source=gbs_api

註釋Attention has more recently been focused on the intermediate semiquinone, detected in the 10-50 ms range using rapid-mix freeze-quench approaches, and shown to accumulate to low-occupancy under conditions in which its oxidation is inhibited. In our 50ms freeze quenched studies, we showed that accumulation of SQo in wild-type occurs only after heme bL is reduced, but that in E295W, accumulation to even higher levels occurs while the heme remains oxidized. This shows that re-duction by SQo is severely inhibited, and allows an estimate of the inhibited rate-constant. Since in this strain, the SQo was constrained to the distal site in which it was generated, the occupancy levels likely reflect an impediment to the diffusional step that accelerates the rate constant by shortening the distance for electron transfer. This inhibition strongly supports a mechanism in which normal forward flux requires migration of SQo within the Qo site (2).^