, Volume 48, Issue 6, pp 770-778

Phylogenetic Analysis of Components of the Eukaryotic Vesicle Transport System Reveals a Common Origin of Adaptor Protein Complexes 1, 2, and 3 and the F Subcomplex of the Coatomer COPI

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


Eukaryotic vesicular transport requires the recognition of membranes through specific protein complexes. The heterotetrameric adaptor protein complexes 1, 2, and 3 (AP1/2/3) are composed of two large, one small, and one medium adaptin subunit. We isolated and characterized the cDNA for Arabidopsisγ-adaptin and performed a phylogenetic analysis of all adaptin subunits (proteins) in the context of all known homologous proteins. This analysis revealed (i) that the large subunits of AP1/2/3 are homologous and (ii) two subunits of the heptameric coatomer I (COPI) complex belong to this gene family. In addition, all small subunits and the aminoterminal domain of the medium subunits of the heterotetramers are homologous to each other; this also holds for two corresponding subunits of the COPI complex. AP1/2/3 and a substructure (heterotetrameric, F-COPI subcomplex) of the heptameric COPI had a common ancestral complex (called pre-F-COPI). Since all large and all small/medium subunits share sequence similarity, the ancestor of this complex is inferred to have been a heterodimer composed of one large and one small subunit. The situation encountered today is the result of successive rounds of coordinated gene duplications of both the large and the small/medium subunits, with F-COPI being the first that separated from the ancestral pre-F-COPI.

Received: 1 October 1998 / Accepted: 4 January 1999