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

J. Biol. Chem., Vol. 279, Issue 28, 28920-28929, July 9, 2004

This Article Full Text Full Text (PDF) All Versions of this Article: 279/28/28920    most recent M313293200v1 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 Bjerkan, T. M. Articles by Valla, S. Search for Related Content PubMed PubMed Citation Articles by Bjerkan, T. M. Articles by Valla, S. Social Bookmarking                      What's this?

The Pseudomonas syringae Genome Encodes a Combined Mannuronan C-5-epimerase and O-Acetylhydrolase, Which Strongly Enhances the Predicted Gel-forming Properties of Alginates^*

Tonje M. Bjerkan, Carol L. Bender, Helga Ertesvåg, Finn Drabløs¶, Mohamed K. Fakhr||, Lori A. Preston**, Gudmund Skjåk-Bræk, and Svein Valla

From the Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway, the Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, Oklahoma 74078, and the ^¶Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, N-7489 Trondheim, Norway

Alginates are industrially important, linear copolymers of -D-mannuronic acid (M) and its C-5-epimer -L-guluronic acid (G). The G residues originate from a postpolymerization reaction catalyzed by mannuronan C-5-epimerases (MEs), leading to extensive variability in M/G ratios and distribution patterns. Alginates containing long continuous stretches of G residues (G blocks) can form strong gels, a polymer type not found in alginate-producing bacteria belonging to the genus Pseudomonas. Here we show that the Pseudomonas syringae genome encodes a Ca²⁺-dependent ME (PsmE) that efficiently forms such G blocks in vitro. The deduced PsmE protein consists of 1610 amino acids and is a modular enzyme related to the previously characterized family of Azotobacter vinelandii ME (AlgE1–7). A- and R-like modules with sequence similarity to those in the AlgE enzymes are found in PsmE, and the A module of PsmE (PsmEA) was found to be sufficient for epimerization. Interestingly, an R module from AlgE4 stimulated Ps-mEA activity. PsmE contains two regions designated M and RTX, both presumably involved in the binding of Ca²⁺. Bacterial alginates are partly acetylated, and such modified residues cannot be epimerized. Based on a detailed computer-assisted analysis and experimental studies another PsmE region, designated N, was found to encode an acetylhydrolase. By the combined action of N and A PsmE was capable of redesigning an extensively acetylated alginate low in G from a non gel-forming to a gel-forming state. Such a property has to our knowledge not been previously reported for an enzyme acting on a polysaccharide.

Received for publication, December 5, 2003 , and in revised form, April 5, 2004.

^* This work was supported by National Institutes of Health Grant AI 43311 (to C. L. B.), FMC Biopolymers, and The Norwegian Research Council. 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 nucleotide sequence(s) reported in this paper has been submitted to the GenBank^TM/EBI Data Bank with accession number(s) AY493437.

^|| Current address: Dept. of Biological Sciences, North Dakota State University, Fargo, ND 58105.

^** Current address: Diversa Corp., 4955 Directors Place, San Diego, CA 92121.

To whom correspondence should be addressed. Tel.: 47-7359-8694; Fax: 47-7359-1283; E-mail: Svein.Valla{at}biotech.ntnu.no.

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

This article has been cited by other articles:

				J. C. Setubal, P. dos Santos, B. S. Goldman, H. Ertesvag, G. Espin, L. M. Rubio, S. Valla, N. F. Almeida, D. Balasubramanian, L. Cromes, et al. Genome Sequence of Azotobacter vinelandii, an Obligate Aerobe Specialized To Support Diverse Anaerobic Metabolic Processes J. Bacteriol., July 15, 2009; 191(14): 4534 - 4545. [Abstract] [Full Text] [PDF]

				W.-S. Chang, M. van de Mortel, L. Nielsen, G. Nino de Guzman, X. Li, and L. J. Halverson Alginate Production by Pseudomonas putida Creates a Hydrated Microenvironment and Contributes to Biofilm Architecture and Stress Tolerance under Water-Limiting Conditions J. Bacteriol., November 15, 2007; 189(22): 8290 - 8299. [Abstract] [Full Text] [PDF]

				M. Gimmestad, M. Steigedal, H. Ertesvag, S. Moreno, B. E. Christensen, G. Espin, and S. Valla Identification and Characterization of an Azotobacter vinelandii Type I Secretion System Responsible for Export of the AlgE-Type Mannuronan C-5-Epimerases. J. Bacteriol., August 1, 2006; 188(15): 5551 - 5560. [Abstract] [Full Text] [PDF]

				F. L. Aachmann, B. I. G. Svanem, P. Guntert, S. B. Petersen, S. Valla, and R. Wimmer NMR Structure of the R-module: A PARALLEL beta-ROLL SUBUNIT FROM AN AZOTOBACTER VINELANDII MANNURONAN C-5 EPIMERASE J. Biol. Chem., March 17, 2006; 281(11): 7350 - 7356. [Abstract] [Full Text] [PDF]

				K. Bakkevig, H. Sletta, M. Gimmestad, R. Aune, H. Ertesvag, K. Degnes, B. E. Christensen, T. E. Ellingsen, and S. Valla Role of the Pseudomonas fluorescens Alginate Lyase (AlgL) in Clearing the Periplasm of Alginates Not Exported to the Extracellular Environment J. Bacteriol., December 15, 2005; 187(24): 8375 - 8384. [Abstract] [Full Text] [PDF]