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

This Article Full Text Full Text (PDF) 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 Sahlman, L. Articles by Powlowski, J. Search for Related Content PubMed PubMed Citation Articles by Sahlman, L. Articles by Powlowski, J. Social Bookmarking                      What's this?

Volume 272, Number 47, Issue of November 21, 1997 pp. 29518-29526
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.

A Mercuric Ion Uptake Role for the Integral Inner Membrane Protein, MerC, Involved in Bacterial Mercuric Ion Resistance

(Received for publication, April 22, 1997, and in revised form, August 20, 1997)

Lena Sahlman , Wendy Wong ^¶ and Justin Powlowski ^¶

From the  Department of Biochemistry, Umeå University, S-901 87, Umeå, Sweden and the ^¶ Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec H3G 1M8, Canada

Bacterial detoxification of mercuric ion depends on the presence of one or more integral membrane proteins (MerT and/or MerC) whose postulated function is in transport of Hg²⁺ from a periplasmic Hg²⁺-binding protein (MerP) to cytoplasmic mercuric reductase. In this study, MerC from the Tn21-encoded mer operon was overexpressed and studied in vesicles and in purified form to clarify the role played by this protein in mercuric ion resistance. MerC-containing vesicles were found to take up mercuric ion independently of MerP. Since uptake correlated with the level of MerC expression was unaffected by osmotic pressure, and was only partially decreased in the presence of 0.05% Triton X-100, the observed uptake appears to represent mainly binding to MerC. Binding was inhibited by thiol-specific reagents, consistent with an essential role for cysteine residues. The essential thiol groups were inaccessible to hydrophilic thiol reagents, whereas hydrophobic reagents completely abolished Hg²⁺ binding. These observations are consistent with the predicted topology of the protein, wherein all 4 cysteine residues are either in the cytoplasm or the bilayer. A role for MerC in Hg²⁺ transport is thus also likely. Based on these results, a modified model for bacterial Hg²⁺ transport is proposed.

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

This article has been cited by other articles:

				R. Thilakaraj, K. Raghunathan, S. Anishetty, and G. Pennathur In silico identification of putative metal binding motifs Bioinformatics, February 1, 2007; 23(3): 267 - 271. [Abstract] [Full Text] [PDF]

				S. Schneiker, M. Keller, M. Droge, E. Lanka, A. Puhler, and W. Selbitschka The genetic organization and evolution of the broad host range mercury resistance plasmid pSB102 isolated from a microbial population residing in the rhizosphere of alfalfa Nucleic Acids Res., December 15, 2001; 29(24): 5169 - 5181. [Abstract] [Full Text] [PDF]

				J. Powlowski and L. Sahlman Reactivity of the Two Essential Cysteine Residues of the Periplasmic Mercuric Ion-binding Protein, MerP J. Biol. Chem., November 19, 1999; 274(47): 33320 - 33326. [Abstract] [Full Text] [PDF]

				C. A. Liebert, R. M. Hall, and A. O. Summers Transposon Tn21, Flagship of the Floating Genome Microbiol. Mol. Biol. Rev., September 1, 1999; 63(3): 507 - 522. [Abstract] [Full Text] [PDF]