PROSITE documentation PDOC51499

APO domain profile

ACCUMULATION OF PHOTOSYSTEM ONE1 (APO1) is required for accumulation of photosystem I (PSI) and other plastid-encoded [4FE-4S] cluster proteins of the chloroplast. APO1 belongs to a gene family with four defined groups (APO1 to APO4) only found in nuclear genomes of vascular plants. Members of the APO gene family are present in both monocotyledonae and dicotydiledonae and are predicted to be localized in chloroplasts and mitochondria. APO1 to APO4 show much fewer similarities in the N terminus than in the remaining part of the proteins, indicating different localizations and/or functions. Each of the groups, APO1 to APO4, displays distinct and conserved features suggesting that they are all important for the plant cell and possess related functions in different cellular compartments [1].

All members of the APO gene family contain an ~100 amino acid residue-spanning region (APO motif 1) with conserved Cys, His, Gly, and acidic and basic amino acids. This highly conserved APO1 motif is duplicated at the C terminus (designated APO motif 2). The two motifs are separated by a non-conserved spacer of variable length. The conserved Cys in both motifs could provide ligands for tetranuclear Fe-S centers. Several conserved differences between the two motifs could indicate different functions. For example, both motifs, APO 1 and 2, contain a conserved H in another positions. Two conserved R residues are present in APO motif 1 and two K residues in motif 2. In addition, APO motif 2 contains conserved G, VW, YG, and A residues, which are not present in APO motif 1 in any of the groups [1].

The profile we developed covers the entire APO domain.