Helix swapping leads to dimerization of the N-terminal domain of the c-type cytochrome maturation protein CcmH from Escherichia coli.
In the process of cytochrome c maturation, heme groups are covalently attached to reduced cysteines of specific heme-binding motifs (CXXCH) in an apocytochrome c sequence. In Escherichia coli, the CcmH protein maintains apo-protein cysteines in a reduced state prior to heme attachment. We have purified and biophysically, as well as structurally characterized the soluble, N-terminal domain of E. coli CcmH that carries the functionally relevant LRCXXC-motif. In contrast to a recently presented structure of the homologous domain from Pseudomonas aeruginosa, the E. coli protein forms a tightly interlinked dimer by swapping its N-terminal helix between two monomers. We propose that an altered environment of the functional motif may help to discern between the two redox partners CcmG and apocytochrome c.
Ahuja
Umesh
U
Institut für Mikrobiologie, Eidgenössische Technische Hochschule, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland. uahuja@ucla.edu
Rozhkova
Anna
A
Glockshuber
Rudolf
R
Thöny-Meyer
Linda
L
Einsle
Oliver
O
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D045304:Cytochromes c / Q000737:chemistry; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D019897:Periplasm / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; C451399:CcmH protein, E coli; D029968:Escherichia coli Proteins; D045304:Cytochromes c; D003545:Cysteine