In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 108, No. 43 ( 2011-10-25), p. 17661-17666
Abstract:
Heme-copper oxidases (HCuOs) are the last components of the respiratory chain in mitochondria and many bacteria. They catalyze O 2 reduction and couple it to the maintenance of a proton-motive force across the membrane in which they are embedded. In the mitochondrial-like, A family of HCuOs, there are two well established proton transfer pathways leading from the cytosol to the active site, the D and the K pathways. In the C family ( cbb 3 ) HCuOs, recent work indicated the use of only one pathway, analogous to the K pathway. In this work, we have studied the functional importance of the suggested entry point of this pathway, the Glu-25 ( Rhodobacter sphaeroides cbb 3 numbering) in the accessory subunit CcoP (E25 P ). We show that catalytic turnover is severely slowed in variants lacking the protonatable Glu-25. Furthermore, proton uptake from solution during oxidation of the fully reduced cbb 3 by O 2 is specifically and severely impaired when Glu-25 was exchanged for Ala or Gln, with rate constants 100–500 times slower than in wild type. Thus, our results support the role of E25 P as the entry point to the proton pathway in cbb 3 and that this pathway is the main proton pathway. This is in contrast to the A-type HCuOs, where the D (and not the K) pathway is used during O 2 reduction. The cbb 3 is in addition to O 2 reduction capable of NO reduction, an activity that was largely retained in the E25 P variants, consistent with a scenario where NO reduction in cbb 3 uses protons from the periplasmic side of the membrane.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.1107543108
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2011
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
Permalink
