Figure 1.

Structural features of the GAS_right TM association motif. (a) The GAS_right motif (which is best known as the fold of the TM region of glycophorin A) is a right-handed helical dimer with a short interhelical distance d and a right-handed crossing angle θ of approximatively −40°. The GxxxG sequence pattern near the crossing point (marked in red in the green helix) allows the backbones to come into close contact. (b) The contact enables the formation of networks of interhelical hydrogen bonds between Cα–H donors and carbonyl oxygen acceptors (shown in detail in (c)).