Isodityrosine Cross-Linking Mediates Insolubilization of Cell Walls in Chlamydomonas

Abstract

Enzymatic removal of the cell wall induces vegetative Chlamydomonas reinhardtii cells to transcribe wall genes and synthesize new hydroxyproline-rich glycoproteins (HRGPs) related to the extensins found in higher plant cell walls. A cDNA expression library made from such induced cells was screened with antibodies to an oligopeptide containing the (SP)x repetitive domains found in Chlamydomonas wall proteins. One of the selected cDNAs encodes an (SP)x-rich polypeptide that also displays a repeated YGG motif. Ascorbate, a peroxidase inhibitor, and tyrosine derivatives were shown to inhibit insolubilization of both the vegetative and zygotic cell walls of Chlamydomonas, suggesting that oxidative cross-linking of tyrosines is occurring. Moreover, insolubilization of both walls was concomitant with a burst in H2O2 production and in extracellular peroxidase activity. Finally, both isodityrosine and dityrosine were found in hydrolysates of the insolubilized vegetative wall layer. We propose that the formation of tyrosine cross-links is essential to Chlamydomonas HRGP insolubilization.

The Chaotrope-soluble Glycoprotein GP2 Is a Precursor of the Insoluble Glycoprotein Framework of the Chlamydomonas Cell Wall

“…As reported previously, the constituents of the insoluble glycoprotein framework of the C. reinhardtii cell wall are cross-linked through the formation of isodityrosine bridges (6) and as a consequence of transglutaminase activity (7). Both cross-linking types are resistant to treatment with HF/pyridine.…”

“…This holds true also for other constituents of the insoluble wall fraction released by chemical deglycosylation (data not shown). These findings are essentially due to the fact that that the constituents of the insoluble wall fraction are cross-linked not only via the HF-sensitive bonds but also via HF-resistant isodityrosine bridges and cross-links formed by the action of transglutaminase (6,7).…”

“…This holds true also for other constituents of the insoluble cell wall fraction released during chemical deglycosylation (data not shown). These findings are at least partly due to the fact that the polypeptide constituents of the insoluble wall fraction are cross-linked not only via the HF-sensitive bonds but also via HF-resistant isodityrosine formation and transglutaminase-dependent reactions (6,7). Therefore, we decided to look for putative precursors of the insoluble glycoprotein framework of the insoluble cell wall fraction.…”

Features of cell metabolism of Chlamydomonas reinhardtii CC-124 wild strain [137c] under mixotrophic and phototrophic cultivation

“…Кроме того, у Ch. reinhardtii клеточная облочка содержит обогащенный тирозином гликопротеин (Waffenschmidt et al, 1993), содержание которого может увеличиваться в качестве адаптивной реакции в связи с изменением условий выращивания.…”

When Simpler Is Better. Unicellular Green Algae for Discovering New Genes and Functions in Carbohydrate Metabolism

“…Analysis of soluble enzyme activity combined with studies in which inhibitors that interfere with crosslinking are applied reveal that a peroxidase and a transglutaminase are involved in wall regeneration (Waffenschmidt et al, 1993(Waffenschmidt et al, , 1999. Because C. rein- Previously characterized mutants (Buleon at el, 1998) illustrate the color-based detection of mutants for altered starch (sta1, no color; sta2, red; sta3, olive; and cc1928 wild type, violet).…”