FIGURE 4.

Ribbon representation of the NMR structure of apoE-NT highlighting the buried H-bonds between different helix-helix interfaces. The side chain heavy atoms of the buried H-bonds are displayed as sticks. The H-bonds are represented by blue dotted lines. The residues in the front helices are colored in green, and the residues in the back helices are in red. The helices are labeled and colored as follows: helices 1 and 4, wheat; helices 2 and 3, light blue; helix 1′, violet; helix N, salmon; helix C, marine blue. A, the buried H-bonds located in the interfaces between helices 1 and 4 and between helices 1′ and 4. No buried H-bonds are found between helices 2 and 3. B, the buried H-bonds located in the interfaces between helices 1 and 2 and between helices 3 and 4. Also shown are the buried H-bonds between helix N/C and the helix bundle.