Crystal structure of the periplasmic domain of CcmH from Pseudomonas aeruginosa

Experimental Data Snapshot

  • Resolution: 1.70 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.209 
  • R-Value Observed: 0.211 

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A strategic protein in cytochrome c maturation: three-dimensional structure of CcmH and binding to apocytochrome c

Di Matteo, A.Gianni, S.Schinina, M.E.Giorgi, A.Altieri, F.Calosci, N.Brunori, M.Travaglini-Allocatelli, C.

(2007) J Biol Chem 282: 27012-27019

  • DOI: https://doi.org/10.1074/jbc.M702702200
  • Primary Citation of Related Structures:  

  • 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.

  • Organizational Affiliation

    Dipartimento di Scienze Biochimiche and Istituto di Biologia e Patologia Molecolari del Consiglio Nazionale delle Ricerche (CNR), La Sapienza, Università di Roma, Piazzale A. Moro 5, 00185 Roma Italy.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cytochrome C-type biogenesis protein CcmH84Pseudomonas aeruginosaMutation(s): 0 
Find proteins for Q9I3N0 (Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1))
Explore Q9I3N0 
Go to UniProtKB:  Q9I3N0
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9I3N0
Sequence Annotations
  • Reference Sequence
Small Molecules
Experimental Data & Validation

Experimental Data

  • Resolution: 1.70 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.209 
  • R-Value Observed: 0.211 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 40.073α = 90
b = 45.414β = 90
c = 48.127γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-07-10
    Type: Initial release
  • Version 1.1: 2007-10-03
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Version format compliance