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) Alert me when this article is cited 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 Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Metcalf, T. Articles by West, C. M. Search for Related Content PubMed PubMed Citation Articles by Metcalf, T. Articles by West, C. M. Agricola Articles by Metcalf, T. Articles by West, C. M.

Formation of the outer layer of the Dictyostelium spore coat depends on the inner-layer protein SP85/PsB

¹ Dept of Anatomy and Cell Biology, ICBR, University of Florida, Gainesville, FL 32610-0235, USA
² College of Medicine and Electron Microscopy Core Laboratory, ICBR, University of Florida, Gainesville, FL 32610-0235, USA

Correspondence
Christopher M. West
westcm{at}ufl.edu

The Dictyostelium spore is surrounded by a 220 µm thick trilaminar coat that consists of inner and outer electron-dense layers surrounding a central region of cellulose microfibrils. In previous studies, a mutant strain (TL56) lacking three proteins associated with the outer layer exhibited increased permeability to macromolecular tracers, suggesting that this layer contributes to the coat permeability barrier. Electron microscopy now shows that the outer layer is incomplete in the coats of this mutant and consists of a residual regular array of punctate electron densities. The outer layer is also incomplete in a mutant lacking a cellulose-binding protein associated with the inner layer, and these coats are deficient in an outer-layer protein and another coat protein. To examine the mechanism by which this inner-layer protein, SP85, contributes to outer-layer formation, various domain fragments were overexpressed in forming spores. Most of these exert dominant negative effects similar to the deletion of outer-layer proteins, but one construct, consisting of a fusion of the N-terminal and Cys-rich C1 domain, induces a dense mat of novel filaments at the surface of the outer layer. Biochemical studies show that the C1 domain binds cellulose, and a combination of site-directed mutations that inhibits its cellulose-binding activity suppresses outer-layer filament induction. The results suggest that, in addition to a previously described early role in regulating cellulose synthesis, SP85 subsequently contributes a cross-bridging function between cellulose and other coat proteins to organize previously unrecognized structural elements in the outer layer of the coat.

This article has been cited by other articles:

				S. L. Repass, R. J. Brady, and T. J. O'Halloran Dictyostelium Hip1r contributes to spore shape and requires epsin for phosphorylation and localization J. Cell Sci., November 15, 2007; 120(22): 3977 - 3988. [Abstract] [Full Text] [PDF]

				T. Metcalf, H. van der Wel, R. Escalante, L. Sastre, and C. M. West Role of SP65 in Assembly of the Dictyostelium discoideum Spore Coat Eukaryot. Cell, July 1, 2007; 6(7): 1137 - 1149. [Abstract] [Full Text] [PDF]

				C. Wang, T. M. Butt, and R. J. S. Leger Colony sectorization of Metarhizium anisopliae is a sign of ageing Microbiology, October 1, 2005; 151(10): 3223 - 3236. [Abstract] [Full Text] [PDF]

				F. Wang, T. Metcalf, H. van der Wel, and C. M. West Initiation of Mucin-type O-Glycosylation in Dictyostelium Is Homologous to the Corresponding Step in Animals and Is Important for Spore Coat Function J. Biol. Chem., December 19, 2003; 278(51): 51395 - 51407. [Abstract] [Full Text] [PDF]