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.
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 Arabidopsis gamma-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.
Schledzewski
K
K
Botanical Institute, Technical University of Braunschweig, Humboldtstrasse 1, 38106 Braunschweig, Germany.
Brinkmann
H
H
Mendel
R R
RR
D033961:Adaptor Protein Complex 1; D033965:Adaptor Protein Complex alpha Subunits; D033982:Adaptor Protein Complex gamma Subunits; D033942:Adaptor Proteins, Vesicular Transport; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D018699:Coated Vesicles / Q000378:metabolism*; D020756:Coatomer Protein; D005057:Eukaryotic Cells / Q000378:metabolism*; D019143:Evolution, Molecular; D008565:Membrane Proteins / Q000235:genetics*; D010802:Phylogeny
D033961:Adaptor Protein Complex 1; D033965:Adaptor Protein Complex alpha Subunits; D033982:Adaptor Protein Complex gamma Subunits; D033942:Adaptor Proteins, Vesicular Transport; D020756:Coatomer Protein; D008565:Membrane Proteins