Structure of the human heterotetramericcis-prenyltransferase complex

The human cis -prenyltransferase (h cis -PT) is an enzymatic complex essential for protein N-glycosylation. Synthesizing the precursor of the glycosyl carrier dolichol-phosphate, we reveal here that h cis -PT exhibits a novel heterotetrameric assembly in solution, composed of two catalytic dehydrodolichyl diphosphate synthase (DHDDS) and two inactive Nogo-B receptor (NgBR) subunits. The 2.3 Å crystal structure of the complex exposes a dimer-of-heterodimers arrangement, with DHDDS C-termini serving as homotypic assembly domains. Furthermore, the structure elucidates the molecular details associated with substrate binding, catalysis, and product length determination. Importantly, the distal C-terminus of NgBR transverses across the heterodimeric interface, directly participating in substrate binding and underlying the allosteric communication between the subunits. Finally, mapping disease-associated h cis -PT mutations involved in blindness, neurological and glycosylation disorders onto the structure reveals their clustering around the active site. Together, our structure of the h cis -PT complex unveils the dolichol synthesis mechanism and its perturbation in disease.