Figure 6. Electrostatic surface potential of CRALBP. The structural model of cellular retinaldehyde-binding protein (CRALBP; PDB entry 1XGH) is that of Liu et al. [40]. Surface regions in red have negative electrostatic potential and are acidic. Those in white have neutral electrostatic potential and those in blue have positive electrostatic potential and are basic. A: The two frames form a stereo pair of the basic face of CRALBP. The basic recess (blue) between the upper and lower lobes of CRALBP is approximately 10 Å in diameter. An Arg-Ala-Arg (RAR) sequence, conserved throughout the CRAL_TRIO protein family, is shown (small patch of circled residues). The retinoid-binding site is covered by the lipid exchange loop (large patch of circled residues). The basic recess may mediate interactions of CRALBP with specific acidic lipids. B: The two images form a stereopair of the acidic face of the protein. Note the (negative) acidic patch (red).