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

J. Biol. Chem., Vol. 282, Issue 51, 37016-37025, December 21, 2007

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 282/51/37016    most recent M708097200v1 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 Google Scholar Google Scholar Articles by Zhao, D. Articles by Rubio, L. M. Search for Related Content PubMed PubMed Citation Articles by Zhao, D. Articles by Rubio, L. M. Social Bookmarking                      What's this?

Evidence for nifU and nifS Participation in the Biosynthesis of the Iron-Molybdenum Cofactor of Nitrogenase^*

From the Department of Plant and Microbial Biology, University of California, Berkeley, California 94720

The nifU and nifS genes encode the components of a cellular machinery dedicated to the assembly of [2Fe-2S] and [4Fe-4S] clusters required for growth under nitrogen-fixing conditions. The NifU and NifS proteins are involved in the production of active forms of the nitrogenase component proteins, NifH and NifDK. Although NifH contains a [4Fe-4S] cluster, the NifDK component carries two complex metalloclusters, the iron-molybdenum cofactor (FeMo-co) and the [8Fe-7S] P-cluster. FeMo-co, located at the active site of NifDK, is composed of 7 iron, 9 sulfur, 1 molybdenum, 1 homocitrate, and 1 unidentified light atom. To investigate whether NifUS are required for FeMo-co biosynthesis and to understand at what level(s) they might participate in this process, we analyzed the effect of nifU and nifS mutations on the formation of active NifB protein and on the accumulation of NifB-co, an isolatable intermediate of the FeMo-co biosynthetic pathway synthesized by the product of the nifB gene. The nifU and nifS genes were required to accumulate NifB-co in a nifN mutant background. This result clearly demonstrates the participation of NifUS in NifB-co synthesis and suggests a specific role of NifUS as the major provider of [Fe-S] clusters that serve as metabolic substrates for the biosynthesis of FeMo-co. Surprisingly, although nifB expression was attenuated in nifUS mutants, the assembly of the [Fe-S] clusters of NifB was compensated by other non-nif machinery for the assembly of [Fe-S] clusters, indicating that NifUS are not essential to synthesize active NifB.

Received for publication, September 28, 2007 , and in revised form, October 24, 2007.

^* This work was supported by NIGMS, National Institutes of Health Grant 35332 (to P. W. L.). 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 Table S1.

¹ To whom correspondence should be addressed: Dept. of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, CA 94720. Tel.: 510-643-3940; Fax: 510-642-4995; E-mail: lrubio{at}nature.berkeley.edu.

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