MOLECULAR CHARACTERIZATION OF THE AP19 GENE FAMILY IN ARABIDOPSIS-THALIANA - COMPONENTS OF THE GOLGI AP-1 CLATHRIN ASSEMBLY PROTEIN COMPLEX

AP19 is the smallest polypeptide component of AP-1, the clathrin assoc iated protein complex found in clathrin-coated vesicles of the Golgi a pparatus. Two genomic clones that encode homologues of AP19 were isola ted from Arabidopsis thaliana (AAp19-1 and AAP19-2). Analysis of their nucleotide sequences predict proteins of 162 and 163 amino acids with m(r) of 18 913 and 18 758 respectively. Amino acid sequence compariso ns with mammalian, yeast and plant clathrin associated sequences indic ates that the Arabidopsis genes encode polypeptides that are more clos ely related to the AP19 proteins associated with clathrin-coated Golgi vesicles than to AP17, which is part of the AP-2 complex of endocytic clathrin-coated pits. Ribonuclease protection assays showed that both genes are expressed in all Arabidopsis tissues throughout development . Constitutive transcription of AAP19-1 was confirmed in transgenic Ar abidopsis seedlings and plants containing an AAP19-1 promoter::beta-gl ucuronidase (GUS) fusion by ribonuclease protection assays and GUS his tochemical staining.