title: Expression, purification, and characterization of the CuA-cytochrome c domain from subunit II of the Bacillus subtilis cytochrome caa3 complex in Escherichia coli.
abstract: Cytochrome caa3 from Bacillus subtilis is a member of the heme-copper oxidase family of integral membrane enzymes that includes mitochondrial cytochrome c oxidase. Subunit II of cytochrome caa3 has an extra 100 amino acids at its C-terminus, relative to its mitochondrial counterpart, and this extension encodes a heme C binding domain. Cytochrome caa3 has many of the properties of the complex formed between mitochondrial cytochrome c and mitochondrial cytochrome c oxidase. To examine more closely the interaction between cytochrome c and the oxidase we have cloned and expressed the Cu(A)-cytochrome c portion of subunit II from the cytochrome caa3 complex of B. subtilis. We are able to express about 2000 nmol, equivalent to 65 mg, of the Cu(A)-cytochrome c protein per litre of Escherichia coli culture. About 500 nmol is correctly targeted to the periplasmic space and we purify 50% of that by a combination of affinity chromatography and ammonium sulfate fractionation. The cytochrome c containing sub-domain is well-folded with a stable environment around the heme C center, as its mid-point potential and rates of reduction are indistinguishable from values for the cytochrome c domain of the holo-enzyme. However, the Cu(A) site lacks copper leading to an inherent instability in this sub-domain. Expression of B. subtilis cytochrome c, as exemplified by the Cu(A)-cytochrome c protein, can be achieved in E. coli, and we conclude that the cytochrome c and Cu(A) sub-domains behave independently despite their close physical and functional association.
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, Ont., Canada K7L 3N6.
authors.forename: Diann
authors.initials: D
authors.lastname: Andrews
authors.forename: Neil R
authors.initials: NR
authors.lastname: Mattatall
authors.forename: Danielle
authors.initials: D
authors.lastname: Arnold
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Hill
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics*; D003001:Cloning, Molecular; D003574:Cytochrome c Group / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification*; D045264:Cytochromes a / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification*; D045266:Cytochromes a3 / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification*; D045304:Cytochromes c / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification
chemical_list: D003574:Cytochrome c Group; D045266:Cytochromes a3; D021122:Protein Subunits; D011994:Recombinant Proteins; C036304:copper cytochrome c; C435384:cytochrome caa(3); D045304:Cytochromes c; D045264:Cytochromes a