Analysis of the respiratory chain of the organism is important fo

Analysis of the respiratory chain of the organism is important for understanding the mechanism of aerobic growth in such environments. However, there Evofosfamide supplier are only a few reports about the bioenergetics of A. pernix. Many bacteria and archaea have 2 to 6 terminal oxidases in the respiratory chain [3]. The heme-copper oxidase superfamily can be classified into 3 subfamilies (A-, B-, and C-type) on

the basis of the amino acid sequence of subunit I [4, 5]. The group of A-type oxidases includes mitochondrial cytochrome aa 3-type cytochrome c oxidase (complex IV) and many other bacterial oxidases. In contrast, B-type oxidases have been identified mainly from extremophiles, including thermophilic bacteria, such as Geobacillus thermodenitrificans (formerly called Bacillus thermodenitrificans) [6, 7] and Thermus thermophilus [8], and archaea, such as Sulfolobus acidocaldarius [9]. check details Analysis of the complete genome sequence of A. pernix has shown that it contains A- and B-type heme-copper terminal oxidases (Figure 1). Ishikawa et al. isolated 2 terminal oxidases from A. pernix and designated them as cytochrome ba 3-type (B-type)

and aa 3-type (A-type) cytochrome c oxidases, SC79 in vitro respectively [10]. Both oxidases have a CuA binding motif, but its substrates have not been identified in the genome sequence. Figure 1 Schematic representation of the respiratory chain of Aeropyrum pernix K1. Genes encoding cytochrome c oxidase and other Fossariinae respiratory components in

the bacterium are indicated. ORFs APE_1719.1, APE_1724.1 and APE_1725 encode the cytochrome c 553 complex which was isolated in this study. ORFs APE_0792.1, APE_0793.1 and APE_0795.1, annotated as aoxABC genes, encode an A-type cytochrome c oxidase, and ORFs APE_1623 and APE_1720 encode a B-type cytochrome c oxidase. In the previous study of Ishikawa et al. (2002), these 2 terminal oxidases were designated as cytochrome aa 3- and ba 3-type cytochrome c oxidase, respectively. An extremely haloalkaliphilic archaeon, Natronomonas pharaonis, uses a blue copper protein named halocyanin as a substrate for the terminal oxidase instead of cytochrome c [11]. In S. acidocaldarius, a blue copper protein named sulfocyanin, which is a part of the SoxM supercomplex, is an intermediate in the electron transfer from the bc 1-analogous complex to the terminal oxidase [12]. However, no genes for blue copper proteins homologous to halocyanin or sulfocyanin have been found in the genome of A. pernix. Therefore, although these oxidases can use N, N, N’, N ‘-tetramethyl- p -phenylenediamine (TMPD) and/or bovine cytochrome c as substrates in vitro, the authentic substrate of the two terminal oxidases is not known. In contrast to terminal oxidases, complex III of archaea is not well-known and a canonical bc 1 complex has not been identified in any archaeal genome [13].

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