2HL7

Crystal structure of the periplasmic domain of CcmH from Pseudomonas aeruginosa

Summary for 2HL7

• Entry DOI: 10.2210/pdb2hl7/pdb
• Descriptor: Cytochrome C-type biogenesis protein CcmH, TETRAETHYLENE GLYCOL (3 entities in total)
• Functional Keywords: three-helices bundle, oxidoreductase
• Biological source: Pseudomonas aeruginosa
• Cellular location: Membrane; Single-pass membrane protein; Periplasmic side (Potential): Q9I3N0
• Total number of polymer chains: 1
• Total formula weight: 10015.14

Authors

Di Matteo, A.,Travaglini-Allocatelli, C.,Gianni, S.,Brunori, M. (deposition date: 2006-07-06, release date: 2007-07-10, Last modification date: 2024-10-16)

Primary citation

Di Matteo, A.,Gianni, S.,Schinina, M.E.,Giorgi, A.,Altieri, F.,Calosci, N.,Brunori, M.,Travaglini-Allocatelli, C.
A strategic protein in cytochrome c maturation: three-dimensional structure of CcmH and binding to apocytochrome c
J.Biol.Chem., 282:27012-27019, 2007

PubMed Abstract: CcmH (cytochromes c maturation protein H) is an essential component of the assembly line necessary for the maturation of c-type cytochromes in the periplasm of Gram-negative bacteria. The protein is a membrane-anchored thiol-oxidoreductase that has been hypothesized to be involved in the recognition and reduction of apocytochrome c, a prerequisite for covalent heme attachment. Here, we present the 1.7A crystal structure of the soluble periplasmic domain of CcmH from the opportunistic pathogen Pseudomonas aeruginosa (Pa-CcmH*). The protein contains a three-helix bundle, i.e. a fold that is different from that of all other thiol-oxidoreductases reported so far. The catalytic Cys residues of the conserved LRCXXC motif (Cys(25) and Cys(28)), located in a long loop connecting the first two helices, form a disulfide bond in the oxidized enzyme. We have determined the pK(a) values of these 2 Cys residues of Pa-CcmH* (both >8) and propose a possible mechanistic role for a conserved Ser(36) and a water molecule in the active site. The interaction between Pa-CcmH* and Pa-apocyt c(551) (where cyt c(551) represents cytochrome c(551)) was characterized in vitro following the binding kinetics by stopped-flow using a Trp-containing fluorescent variant of Pa-CcmH* and a dansylated peptide, mimicking the apocytochrome c(551) heme binding motif. The kinetic results show that the protein has a moderate affinity to its apocyt substrate, consistent with the role of Pa-CcmH as an intermediate component of the assembly line for c-type cytochrome biogenesis.

PubMed: 17623665
DOI: 10.1074/jbc.M702702200

Experimental method

X-RAY DIFFRACTION (1.7 Å)