The High-Molecular-Weight Cytochrome c Cyc2 of Acidithiobacillus ferrooxidans Is an Outer Membrane Protein

Abstract

A high-molecular-weight c-type cytochrome, Cyc2, and a putative 22-kDa c-type cytochrome were detected in the membrane fraction released during spheroplast formation from Acidithiobacillus ferrooxidans. This fraction was enriched in outer membrane components and devoid of cytoplasmic membrane markers. The genetics, as well as the subcellular localization of Cyc2 at the outer membrane level, therefore make it a prime candidate for the initial electron acceptor in the respiratory pathway between ferrous iron and oxygen.

Metabolic diversity among main microorganisms inside an arsenic-rich ecosystem revealed by meta- and proteo-genomics

“…ferrooxidans. Cyc1 belongs to the c4 family and Cyc2 is an outer membrane cytochrome c proposed to receive electrons directly from ferrous iron (Yarzabal et al, 2002). Even though the other genes of the rus operon known to be involved in the electron transfer between Fe(II) and oxygen in At.…”

The Multicenter Aerobic Iron Respiratory Chain of Acidithiobacillus ferrooxidans Functions as an Ensemble with a Single Macroscopic Rate Constant

“…The rus operon is hypothesized to encode all of the principal electron transport proteins that compose the iron respiratory chain (15). The primary oxidation of extracellular ferrous iron is thought to be accomplished by an outer membrane cytochrome c (7,12) that passes the electrons to rusticyanin, a type I blue copper protein located in the periplasmic space of this Gram-negative organism (1,24). These electrons are then transferred from the rusticyanin via a different periplasmic cytochrome c (14) to an aa 3 -type terminal oxidase that spans the cytoplasmic membrane and transfers electrons to molecular oxygen (6,13).…”

“…A number of laboratories have described redox-active proteins expressed by At. ferrooxidans that might participate in the iron respiratory chain (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Perhaps the most generally accepted model for the iron respiratory chain of At.…”

Reduction of Hg2+with Reduced Mammalian Cytochromecby CytochromecOxidase Purified from a Mercury-ResistantAcidithiobacillus ferrooxidansStrain, MON-1

“…Although the same amounts of ferrous iron were oxidized when strains MON-1 and ATCC 23270 gave maximum cell yields, the growth yield of strain MON-1 was It is well known that aa 3 type cytochrome c oxidase is one of the most important components of the iron oxidation enzyme system in A. ferrooxidans. 32,[35][36][37][38][39][40][41][42][43][44] We have found that mercury resistant-A. ferrooxidans strains SUG 2-2 and MON-1 have high Fe 2þ -dependent mercury volatilization activity in the cells, 30,31) and that cytochrome c oxidase purified from strain SUG 2-2 reduces Hg 2þ with Fe 2þ as electron donor volatilizing metalic mercury (Hg 0 ) outside of the cells.…”