This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (60) Citing Articles via Google Scholar Google Scholar Articles by Stafstrom, J. P. Articles by Staehelin, L. A. Search for Related Content PubMed PubMed Citation Articles by Stafstrom, J. P. Articles by Staehelin, L. A. Agricola Articles by Stafstrom, J. P. Articles by Staehelin, L. A.

Articles

Cross-Linking Patterns in Salt-Extractable Extensin from Carrot Cell Walls ¹

Department of Molecular, Cellular and Developmental Biology, Campus Box 347, University of Colorado, Boulder, Colorado 80309

Extensins are hydroxyproline-rich glycoproteins (HRGPs) found in the primary cell walls of dicots. Extensin monomers are secreted into the wall and covalently bound to each other, presumably by isodityrosine (IDT) cross-links, to form a rigid matrix. Expression of the extensin matrix is correlated with inhibition of cell elongation during normal development and with increased resistance to virulent pathogens. We have isolated extensin from carrot root tissue (Daucus carota L.) by published techniques and have used gel filtration chromatography to purify fractions enriched in monomers and oligomers. We refer to this protein as "extensin-1" to distinguish it from "extensin-2," a second extensin-like HRGP from carrot which we will describe later. We prepared extensin-1 for electron microscopy by shadowing it with platinum. Monomers are highly elongated (84 nanometers) and kinked at several sites. Kinks occur at all sites on molecules with nearly equal probability, but do not appear to occur at their ends. The distribution of kinks is similar to that of tyrosine-lysine-tyrosine sequences, which have been shown to be capable of forming intramolecular IDT cross-links, so we suggest that kinks are visible manifestations of intramolecular IDTs. Oligomers likely result from IDT cross-links between monomers, and may be regarded as transient precursors of the fully cross-linked matrix. Nearly 60% of cross-links involve the ends of molecules while the rest are scattered among internal sites. We discuss how the relative positions and proportions of intra- and intermolecular cross-links in extensin-1 may affect the structure, and in turn the function, of the extensin matrix.

¹ Supported by National Institutes of Health grant GM 18639 to L. A. Staehelin.

This article has been cited by other articles:

				M. C. Cannon, K. Terneus, Q. Hall, L. Tan, Y. Wang, B. L. Wegenhart, L. Chen, D. T. A. Lamport, Y. Chen, and M. J. Kieliszewski Self-assembly of the plant cell wall requires an extensin scaffold PNAS, February 12, 2008; 105(6): 2226 - 2231. [Abstract] [Full Text] [PDF]

				M. J. Kieliszewski, M. O'Neill, J. Leykam, and R. Orlando Tandem Mass Spectrometry and Structural Elucidation of Glycopeptides from a Hydroxyproline-rich Plant Cell Wall Glycoprotein Indicate That Contiguous Hydroxyproline Residues Are the Major Sites of Hydroxyproline O-Arabinosylation J. Biol. Chem., February 10, 1995; 270(6): 2541 - 2549. [Abstract] [Full Text] [PDF]