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

J. Biol. Chem., Vol. 280, Issue 46, 38513-38521, November 18, 2005

This Article Full Text Full Text (PDF) All Versions of this Article: 280/46/38513    most recent M508449200v1 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 Li, J. S. Articles by Li, J. Search for Related Content PubMed PubMed Citation Articles by Li, J. S. Articles by Li, J. Social Bookmarking                      What's this?

Novel Glycosidic Linkage in Aedes aegypti Chorion Peroxidase

N-MANNOSYL TRYPTOPHAN^*

Junsuo S. Li, Liwang Cui, Daniel L. Rock, and Jianyong Li1

From the Department of Pathobiology, University of Illinois, Urbana, Illinois 61802 and the Department of Entomology, Pennsylvania State University, University Park, Pennsylvania 16802

Aedes aegypti chorion peroxidase (CPO) plays a crucial role in chorion hardening by catalyzing chorion protein cross-linking through dityrosine formation. The enzyme is extremely resistant to denaturing conditions, which seem intimately related to its post-translational modifications, including disulfide bond formation and glycosylation. In this report, we have provided data that describe a new type of glycosylation in CPO, where a mannose is linked to the N-1 atom of the indole ring of Trp residue. Through liquid chromatography/electrospray ionization/tandem mass spectrometry and de novo sequencing of CPO tryptic peptides, we determined that three of the seven available Trp residues in mature CPO are partially (40–50%) or completely mannosylated. This conclusion is based on the following properties of the electrospray ionization/tandem mass spectrometry spectra and the enzymatic reaction of these peptides: 1) the presence of a 162-Da substituent in each Trp residue; 2) the presence of abundant fragments of m/z 163 ([Hex + H]) and [M + H - 162] (typical for N-glycosides); 3) the absence of a loss of 120 Da (this loss is typical for aromatic C-glycosides); and 4) the cleavage of the glycosidic linkage by PNGase A or F (typical for N-glycans). These results establish that a C–N bond is formed between the anomeric carbon of a mannose residue and the N-1 atom of the indole ring of Trp. This is the first report that provides definitive evidence for N-mannosylation of Trp residues in a protein. In addition, our data demonstrate that PNGase can hydrolyze Trp N-linked mannose in peptides, which is unusual because no typical -amide bond is present in the Trp-mannosyl moiety. Results of this study should stimulate research toward a comprehensive understanding of physiology and biochemistry of Trp N-mannosylation in proteins and the overall biochemical mechanisms of PNGase-catalyzed reactions.

Received for publication, August 1, 2005 , and in revised form, September 2, 2005.

^* This work was supported by National Institutes of Health Grant AI 37789. 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.

¹ To whom correspondence should be addressed: Dept. of Pathobiology, University of Illinois, 2001 S. Lincoln Ave., Urbana, IL 61802. Tel.: 217-244-3913; E-mail: jli2{at}uiuc.edu.

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