title: Structural insights into lipid-dependent reversible dimerization of human GLTP.
abstract: Human glycolipid transfer protein (hsGLTP) forms the prototypical GLTP fold and is characterized by a broad transfer selectivity for glycosphingolipids (GSLs). The GLTP mutation D48V near the `portal entrance' of the glycolipid binding site has recently been shown to enhance selectivity for sulfatides (SFs) containing a long acyl chain. Here, nine novel crystal structures of hsGLTP and the SF-selective mutant complexed with short-acyl-chain monoSF and diSF in different crystal forms are reported in order to elucidate the potential functional roles of lipid-mediated homodimerization. In all crystal forms, the hsGLTP-SF complexes displayed homodimeric structures supported by similarly organized intermolecular interactions. The dimerization interface always involved the lipid sphingosine chain, the protein C-terminus (C-end) and α-helices 6 and 2, but the D48V mutant displayed a `locked' dimer conformation compared with the hinge-like flexibility of wild-type dimers. Differences in contact angles, areas and residues at the dimer interfaces in the `flexible' and `locked' dimers revealed a potentially important role of the dimeric structure in the C-end conformation of hsGLTP and in the precise positioning of the key residue of the glycolipid recognition centre, His140. ΔY207 and ΔC-end deletion mutants, in which the C-end is shifted or truncated, showed an almost complete loss of transfer activity. The new structural insights suggest that ligand-dependent reversible dimerization plays a role in the function of human GLTP.
authors.affiliation: Structural Biology Unit, CIC bioGUNE, Technology Park of Bizkaia, 48160 Derio, Spain.
authors.forename: Valeria R
authors.initials: VR
authors.lastname: Samygina
authors.forename: Borja
authors.initials: B
authors.lastname: Ochoa-Lizarralde
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Popov
authors.forename: Aintzane
authors.initials: A
authors.lastname: Cabo-Bilbao
authors.forename: Felipe
authors.initials: F
authors.lastname: Goni-de-Cerio
authors.forename: Julian G
authors.initials: JG
authors.lastname: Molotkovsky
authors.forename: Dinshaw J
authors.initials: DJ
authors.lastname: Patel
authors.forename: Rhoderick E
authors.initials: RE
authors.lastname: Brown
authors.forename: Lucy
authors.initials: L
authors.lastname: Malinina
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D018360:Crystallography, X-Ray; D006028:Glycosphingolipids / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D006801:Humans; D008024:Ligands; D050356:Lipid Metabolism / Q000502:physiology*; D011485:Protein Binding; D017510:Protein Folding; D055503:Protein Multimerization / Q000502:physiology*; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
chemical_list: D002352:Carrier Proteins; C511922:GLTP protein, human; D006028:Glycosphingolipids; D008024:Ligands
keywords: GLTP fold; glycolipid transfer protein; lipid-mediated homodimerization; selectivity; sulfatides