Title : Endogenous phosphatidylcholine and a long spacer ligand stabilize the lipid-binding groove of
CD1b
Abstract :
- CD1 proteins present lipid antigens to T cells
- The antigens are acquired in the endosomal compartments
- This raises the question of how the large hydrophobic CD1 pockets are preserved between the moment of biosynthesis in the endoplasmic reticulum and arrival to the endosomes
- To address this issue, the natural ligands associated with a soluble form of human CD1b have been investigated
- Using isoelectric focusing, native mass spectrometry and resolving the crystal structure at 1.8 A resolution, we found that human CD1b is simultaneously associated with endogenous phosphatidylcholine (PC) and a 41-44 carbon atoms-long spacer molecule
- The two lipids appear to work in concert to stabilize the CD1b groove, their combined size slightly exceeding the maximal groove capacity
- We propose that the spacer serves to prevent binding of ligands with long lipid tails , whereas short- chain lipids might still displace the PC, which is exposed at the groove entrance
- The data presented herein explain how the CD1b groove is preserved, and provide a rationale for the in vivo antigen-binding properties of CD1b
Output (sent_index, trigger,
protein,
sugar,
site):
Output(Part-Of) (sent_index,
protein,
site):
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):