dolicololfosfato

Dolicololfosfato, also known as dolichol phosphate in some contexts, is a long-chain polyisoprenoid lipid that contains a single phosphate head group. It functions as a lipid carrier embedded in the endoplasmic reticulum (ER) membrane and is essential for the co-translational and post-translational processing of proteins through N-linked glycosylation in eukaryotes.

In the N-linked glycosylation pathway, dolichol phosphate serves as the initial carrier to assemble the lipid-linked oligosaccharide donor that is later transferred en bloc to specific asparagine residues on nascent polypeptides. The process begins with the transfer of N-acetylglucosamine-1-phosphate to dolichol phosphate by the enzyme UDP-GlcNAc:dolichyl-phosphate N-acetylglucosamine-1-phosphate transferase, forming GlcNAc-PP-dolichol. Subsequent steps add mannose units and glucose units from donor molecules that derive from dolichol phosphate derivatives (for example, dolichol phosphate mannose and dolichol phosphate glucose). The final lipid-linked oligosaccharide is typically Glc3Man9GlcNAc2-PP-dolichol. The oligosaccharide is then transferred to an asparagine residue of a protein by the oligosaccharyltransferase complex, releasing dolichol phosphate to re-enter the cycle.

Structure and localization can vary among species, but the molecule is consistently a hydrophobic, long-chain lipid with a phosphate head group, concentrated in ER membranes where glycoprotein maturation occurs. Disruptions in dolichol phosphate synthesis or recycling can lead to congenital disorders of glycosylation, reflecting its central role in protein maturation and cellular function.