The SEC7 domain was named after the first protein found to contain such a
region . SEC7 family proteins are guanine nucleotide exchange factor (GEF)
specific for the ADP-rybosylation factors (ARF), a Ras-like GTPases which is
important for vesicular protein trafficking. Although SEC7 proteins are highly
divergent in their overall sequence they share a common region of roughly 200
amino acids known as the SEC7 domain. Proteins containing a SEC7 domain are
found in fungi, animals and plants.
SEC7 domains mediate interaction with ARF and catalyses GDP to GTP exchange
[2,3,4]. Crystal structure of the human ARNO SEC7 domain has been solved [5,6]
and consist of 10 α-helices. The helices are arranged in a right-handed
superhelix reminiscent of that found in the armadillo-repeat (see
<PDOC50176>). The C-terminal part of the domain mediates interaction with
Arf-1 through hydrophobic and polar residues. The nucleotide exchange activity
is dependent on a conserved glutamate residue located in the loop between
helix f and g [5,6]. The corresponding residue in Arabidopsis Emb30 protein is
mutated to a lysine in a deficient allele .
Some proteins known to contain a SEC7 domain are listed below.
Yeast SEC7 protein. Associated with ER, essential for fusion of vesicles to
Mammalian cytohesin 1.
Mammalian cytohesin 2 (ARF nucleotide-binding site opener; ARNO).
Mammalian cytohesin 3.
Mammalian cytohesin 4.
Mammalian brefeldin A-inhibited guanine nucleotide-exchange proteins 1 and
2 (ARFGEP1 and ARFGEP2).
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