Figure 4.

The N-Terminal Part of SEC7 Is Required for the Heterotypic Interaction but Not for the Catalytic Exchange Reaction.

(A) Interallelic complementation assay. Seedling phenotypes of gnom homozygous mutants (top panels): gnom^G579R (left; bar = 0.05 mm), gnom^G568R (right; bar = 2.5 mm); and gnom trans-heterozygotes (lower panel): gnom^G568R/gnom^G579R (left; bar = 2.5 mm) and gnom^G568R/gnom^E658K (right; bar = 3 mm).

(B) In vitro catalytic exchange activity of the SEC7 domain of BIG3 harboring a single amino acid exchange mutation. The GDP/GTP exchange activity of His-SEC7^BIG3 (1; blue) and His-SEC7^BIG3G626R (2; red) were measured on ARF1. Negative control: ARF1 alone (3; black).