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

J. Biol. Chem., Vol. 282, Issue 4, 2494-2504, January 26, 2007

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 282/4/2494    most recent M608615200v1 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 Sidhu, A. B. S. Articles by Fidock, D. A. Search for Related Content PubMed PubMed Citation Articles by Sidhu, A. B. S. Articles by Fidock, D. A. Social Bookmarking                      What's this?

In Vitro Efficacy, Resistance Selection, and Structural Modeling Studies Implicate the Malarial Parasite Apicoplast as the Target of Azithromycin^*

Amar Bir Singh Sidhu, Qingan Sun, Louis J. Nkrumah, Michael W. Dunne^¶, James C. Sacchettini, and David A. Fidock¹

From the Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461, the Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, and ^¶Pfizer Global Research and Development, Pfizer Inc., New London, Connecticut 06320

Azithromycin (AZ), a broad-spectrum antibacterial macrolide that inhibits protein synthesis, also manifests reasonable efficacy as an antimalarial. Its mode of action against malarial parasites, however, has remained undefined. Our in vitro investigations with the human malarial parasite Plasmodium falciparum document a remarkable increase in AZ potency when exposure is prolonged from one to two generations of intraerythrocytic growth, with AZ producing 50% inhibition of parasite growth at concentrations in the mid to low nanomolar range. In our culture-adapted lines, AZ displayed no synergy with chloroquine (CQ), amodiaquine, or artesunate. AZ activity was also unaffected by mutations in the pfcrt (P. falciparum chloroquine resistance transporter) or pfmdr1 (P. falciparum multidrug resistance-1) drug resistance loci, as determined using transgenic lines. We have selected mutant, AZ-resistant 7G8 and Dd2 parasite lines. In the AZ-resistant 7G8 line, the bacterial-like apicoplast large subunit ribosomal RNA harbored a U438C mutation in domain I. Both AZ-resistant lines revealed a G76V mutation in a conserved region of the apicoplast-encoded P. falciparum ribosomal protein L4 (PfRpl4). This protein is predicted to associate with the nuclear genome-encoded P. falciparum ribosomal protein L22 (PfRpl22) and the large subunit rRNA to form the 50 S ribosome polypeptide exit tunnel that can be occupied by AZ. The PfRpl22 sequence remained unchanged. Molecular modeling of mutant PfRpl4 with AZ suggests an altered orientation of the L75 side chain that could preclude AZ binding. These data imply that AZ acts on the apicoplast bacterial-like translation machinery and identify Pfrpl4 as a potential marker of resistance.

Received for publication, September 6, 2006 , and in revised form, November 6, 2006.

^* This work was supported by a collaborative research agreement between Pfizer Inc. and the Albert Einstein College of Medicine. 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 supplemental Figs. 1–2 and Tables 1–3.

¹ To whom correspondence should be addressed: Forchheimer 403, 1300 Morris Park Ave., Bronx, NY 10461. Tel.: 718-430-3759; Fax: 718-430-8711; E-mail: dfidock{at}aecom.yu.edu.

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

This article has been cited by other articles:

				D. Barthel, M. Schlitzer, and G. Pradel Telithromycin and Quinupristin-Dalfopristin Induce Delayed Death in Plasmodium falciparum Antimicrob. Agents Chemother., February 1, 2008; 52(2): 774 - 777. [Abstract] [Full Text] [PDF]

				R. Binet and A. T. Maurelli Frequency of Development and Associated Physiological Cost of Azithromycin Resistance in Chlamydia psittaci 6BC and C. trachomatis L2 Antimicrob. Agents Chemother., December 1, 2007; 51(12): 4267 - 4275. [Abstract] [Full Text] [PDF]

				E. L. Dahl and P. J. Rosenthal Multiple Antibiotics Exert Delayed Effects against the Plasmodium falciparum Apicoplast Antimicrob. Agents Chemother., October 1, 2007; 51(10): 3485 - 3490. [Abstract] [Full Text] [PDF]