| Autor: |
Laratta WP; Department of Microbiology, Wing Hall, Cornell University, Ithaca, NY 14850-8101, USA., Nanaszko MJ; Department of Microbiology, Wing Hall, Cornell University, Ithaca, NY 14850-8101, USA., Shapleigh JP; Department of Microbiology, Wing Hall, Cornell University, Ithaca, NY 14850-8101, USA. |
| Jazyk: |
angličtina |
| Zdroj: |
Microbiology (Reading, England) [Microbiology (Reading)] 2006 May; Vol. 152 (Pt 5), pp. 1479-1488. |
| DOI: |
10.1099/mic.0.28524-0 |
| Abstrakt: |
The role of cytochrome c(2), encoded by cycA, and cytochrome c(Y), encoded by cycY, in electron transfer to the nitrite reductase of Rhodobacter sphaeroides 2.4.3 was investigated using both in vivo and in vitro approaches. Both cycA and cycY were isolated, sequenced and insertionally inactivated in strain 2.4.3. Deletion of either gene alone had no apparent effect on the ability of R. sphaeroides to reduce nitrite. In a cycA-cycY double mutant, nitrite reduction was largely inhibited. However, the expression of the nitrite reductase gene nirK from a heterologous promoter substantially restored nitrite reductase activity in the double mutant. Using purified protein, a turnover number of 5 s(-1) was observed for the oxidation of cytochrome c(2) by nitrite reductase. In contrast, oxidation of c(Y) only resulted in a turnover of approximately 0.1 s(-1). The turnover experiments indicate that c(2) is a major electron donor to nitrite reductase but c(Y) is probably not. Taken together, these results suggest that there is likely an unidentified electron donor, in addition to c(2), that transfers electrons to nitrite reductase, and that the decreased nitrite reductase activity observed in the cycA-cycY double mutant probably results from a change in nirK expression. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
|
