Fig. 2. Structure of the START domains of MLN64 (A) and PCTP with its ligand (B). (A) Ribbon diagram of the START domain of MLN64 (PDB ID code: 1EM2). Secondary structural elements and the C- and N-termini are labeled. MLN64 has a central ß-sheet (yellow) gripped by N-terminal (1) and C-terminal (4) -helices (red), the latter being closely packed above the curved sheet. (B). Cut-away view of the molecular surface of the START domain of PCTP complexed with a phosphatidylcholine molecule (DLPC, dilinoleoyl-sn-glycerol-3-phosphorylcholine) (PDB ID code: 1LN1). The DLPC molecule (shown in stick representation) is located in the hydrophobic tunnel formed in the START domain. The orientation of the START domain is similar to that in A. The protein surface is colored according to secondary structure: red for helices, yellow for ß strands and green for loops. These figures were prepared with PyMOL software (W. L. DeLano, 2002, The PyMOL molecular graphics system. http://www.pymol.org).