Nucleotide-sugar transporters (NSTs) are localised in membranes of the Golgi apparatus and endoplasmatic reticulum. NSTs transport sugar nucleotides from the cytoplasm into the organelle’s lumen, where they are used for the biosynthesis of glycoproteins and glycolipids.
A recent work presented the first crystal structure of a mouse CMP-sialic acid transporter (CST) in complex with its substrates. This NST is an antiporter and a member of solute carrier family that translocates CMP-sialic acid in the Golgi lumen in exchange for CMP. It regulates the sialylation of glycoconjugates and is linked to the congenital disorder of glycosylation.
The CST was overexpressed in yeast (Pichia pastoris), purified by non-denaturing detergent treatment (n-dodecyl-β-maltopyranoside) and crystallised. Visualisation of the CST in complex with its substrates, CMP-sialic acid (from Carbosynth) and CMP, revealed the mechanisms behind substrate selectivity.
For more details on the findings, read the original paper published in eLife: Ahuja and Whorton, 2019.