Nonenzymatic synthesis of anomerically pure, mannosyl-based molecular probes for scramblase identification studies.

Giovanni Picca,Markus Probst,Anant K Menon,Robert Häner,Simon M Langenegger,Peter Bütikofer,Oleg Khorev

doi:10.3762/bjoc.16.145

Giovanni Picca, Markus Probst + Show 5 more

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https://doi.org/10.3762/bjoc.16.145

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Abstract

The chemical synthesis of molecular probes to identify and study membrane proteins involved in the biological pathway of protein glycosylation is described. Two short-chain glycolipid analogs that mimic the naturally occurring substrate mannosyl phosphoryl dolichol exhibit either photoreactive and clickable properties or allow the use of a fluorescence readout. Both probes consist of a hydrophilic mannose headgroup that is linked to a citronellol derivative via a phosphodiester bridge. Moreover, a novel phosphoramidite chemistry-based method offers a straightforward approach for the non-enzymatic incorporation of the saccharide moiety in an anomerically pure form.

Highlights

Mannosyl phosphoryl dolichol (MPD), an important, multifunctional glycolipid, is used as a mannose donor for protein N-glycosylation, O- and C-mannosylation, and glycosylphosphatidylinositol (GPI) anchoring in the luminal leaflet of the endoplasmic reticulum (ER) [1,2,3,4,5,6,7,8]
The synthesis of the target compounds MPC-1 and MPC-2 started from commercially available (S)-citronellol (Cit), 4,4′dihydroxybenzophenone (BZP), D-mannose (Man), and 1,12dodecanediol (Dod, Figure 2)
While there are no noteworthy difficulties in the synthesis of the molecular probe MPC-1 to report, the same cannot be said for MPC-2

Summary

Introduction

Mannosyl phosphoryl dolichol (MPD), an important, multifunctional glycolipid, is used as a mannose donor for protein N-glycosylation, O- and C-mannosylation, and glycosylphosphatidylinositol (GPI) anchoring in the luminal leaflet of the endoplasmic reticulum (ER) [1,2,3,4,5,6,7,8]. MPD is synthesized on the cytoplasmic face of the ER and must be translocated across the ER membrane to participate in luminal glycosyltransfer reactions [3,4]. A specific membrane protein – MPD scramblase – is required to facilitate the transbilayer movement of MPD across the ER. The activity of MPD scramblase has been described in microsomal vesicles and reconstituted systems [1,2,9], the molecular identity of this protein remains unknown.

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