Glycolipid transfer protein GLTP
Bos taurus (bovine)
Glycolipid, one of the membrane components, is a kind of lipid which has one or more sugar residues. Glycolipids participate in many important cellular processes including development, adhesion and cell-cell recognition both in eukaryotes and prokaryotes. For example, differences between ABO blood type are differences between sugar residues of glycolipid which is on the surface of red blood cells. Most glycolipids are synthesized on the luminal side of the Golgi, however, precursors of glycolipids on the cytosolic surface of the Golgi membrane. Glycolipid transfer protein (GLTP), a 24kDa basic cytosolic protein, is believed to participate in the transfer of this precursor of glycolipids from the cytosolic surface to the luminal side. GLTPs recognize a wide range of different glycolipids and have a high ganglioside transfer activity.
The structure shown here is that of the apo-conformation of bovine GLTP. Two layers of helices are made up of 8 alpha-helices. An acyl chain cavity is located between the alpha-1, alpha-7 and alpha-8 helices, and a sugar-binding pocket is located between the alpha-2 and alpha-4 helices. The authors also propose a glycolipid-bound structure (xPSSS:2BV7) and an intermediate structure (xPSSS:1TFJ). In both the intermediate structure and the apo-state structure, the connection between the acyl chain cavity and the sugar binding pocket is blocked by the side-chain of Ile45 and Phe148 from alpha-2 helix and alpha-6 helix. The authors suggests that during structural changes, the connecting channel between the acyl chain cavity and the sugar binding pocket widens gradually.
Protein Data Bank (PDB)
author: Miho Higurashi