The Post-Translational Modifications, Localization, and Mode of Attachment of Non-Covalently Bound Glucanosyltransglycosylases of Yeast Cell Wall as a Key to Understanding their Functioning.

Glucan linked to proteins is a natural mega-glycoconjugate (mGC) playing the central role as a structural component of a yeast cell wall (CW). Regulation of functioning of non-covalently bound glucanosyltransglycosylases (ncGTGs) that have to remodel mGC to provide CW extension is poorly understood. We demonstrate that the main ncGTGs Bgl2 and Scw4 have phosphorylated and glutathionylated residues and are represented in CW as different pools of molecules having various firmness of attachment. Identified pools contain Bgl2 molecules with unmodified peptides, but differ from each other in the presence and combination of modified ones, as well as in the presence or absence of other CW proteins. Correlation of Bgl2 distribution among pools and its N-glycosylation was not found. Glutathione affects Bgl2 conformation, probably resulting in the mode of its attachment and enzymatic activity. Bgl2 from the pool of unmodified and monophosphorylated molecules demonstrates the ability to fibrillate after isolation from CW. Revealing of Bgl2 microcompartments and their mosaic arrangement summarized with the results obtained give the evidence that the functioning of ncGTGs in CW can be controlled by reversible post-translational modifications and facilitated due to their compact localization. The hypothetical scheme of distribution of Bgl2 inside CW is represented.