HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 282, Issue 37, 27012-27019, September 14, 2007

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 282/37/27012    most recent M702702200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Di Matteo, A. Articles by Travaglini-Allocatelli, C. Search for Related Content PubMed PubMed Citation Articles by Di Matteo, A. Articles by Travaglini-Allocatelli, C. Related Collections Papers Of The Week Social Bookmarking                      What's this?

A Strategic Protein in Cytochrome c Maturation

THREE-DIMENSIONAL STRUCTURE OF CcmH AND BINDING TO APOCYTOCHROME c^*

From the 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

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 1.7Å 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 (Cys²⁵ and Cys²⁸), 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 Ser³⁶ and a water molecule in the active site. The interaction between Pa-CcmH^* and Pa-apocyt c₅₅₁ (where cyt c₅₅₁ represents cytochrome c₅₅₁) 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 c₅₅₁ 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.

Received for publication, March 29, 2007 , and in revised form, May 21, 2007.

The atomic coordinates and structure factors (code 2HL7) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).

^* This work was supported by grants from the Italian Ministero dell'Universitàe della Ricerca (Grant RBLA03B3KC_004 and RBIN040PWNC (to M. B.) and RBIN04T7MT_001 (to M. E. S.) and Grant 2005027330_005 to C. T. A.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains two supplemental figures.

This article was selected as a Paper of the Week.

¹ To whom correspondence should be addressed. E-mail: maurizio.brunori{at}uniroma1.it.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				C. Sanders, S. Turkarslan, D.-W. Lee, O. Onder, R. G. Kranz, and F. Daldal The Cytochrome c Maturation Components CcmF, CcmH, and CcmI Form a Membrane-integral Multisubunit Heme Ligation Complex J. Biol. Chem., October 31, 2008; 283(44): 29715 - 29722. [Abstract] [Full Text] [PDF]