Figure 5
Modeling RAID-RACK1 interactions. (a) Surface representation of RAID1 core segment, Asn-22 to Leu-38, as a helix, with sidechains curtailed at the Cβ atom for clarity. Residues implicated in RACK1 binding are colour-coded on a yellow helical background; blueAsn-22, Pro-23, Trp-24, Asn-26, Arg-34, and purple Leu-29, Val-30, Leu-33, Leu-37, Leu-38. These residues tend to align along one side of the helix. (b) Gβ (blue) – Gγ (yellow) interactions from protein data bank coordinate set '1got,' with a molecular surface (white) drawn for the WD repeats 5–7 of Gβ (lacking the initial β-strand of WD repeat 5 that is associated with the previous propeller blade). (c) Electrostatic potential surface of comparative modeled RACK1 WD repeats 5–7 (equivalent part and in the same orientation as that drawn for Gβ in panel b). Red denotes negative, blue positive, and white is non-polar. (d) RACK1 mutations that affect RAID binding are drawn in green on a molecular surface for WD repeats 5–7. (e) Model for RACK1-RAID interactions, with the core RAID segment of panel a forming the right-hand helix, that connects through a loop to a positive region of RAID that is modeled (left-hand helix) into a negative part of the RACK1 surface. Colour coding for the RACK1 surface follows that in panel 2, and that for the core RAID segment follows panel a. Arg-34 is at the back of the helical ribbon and not visible in this view. The orientation matches panels b,c, and d, so that general features can be compared with Gβ-Gγ.