MOLECULAR CHARACTERIZATION OF 2 HUMAN AUTOANTIGENS - UNIQUE CDNAS ENCODING 95-KD AND 160-KD PROTEINS OF A PUTATIVE FAMILY IN THE GOLGI-COMPLEX

Serum autoantibodies from a patient with autoantibodies directed again st the Golgi complex were used to screen clones from a HepG2 lambdaZap cDNA library. Three related clones, designated SY2, SY10, and SY11, e ncoding two distinct polypeptides were purified for further analysis. Antibodies affinity purified by adsorption to the lambdaZap-cloned rec ombinant proteins and antibodies from NZW rabbits immunized with purif ied recombinant proteins reproduced Golgi staining and bound two diffe rent proteins, 95 and 160 kD, from whole cell extracts. The SY11 prote in was provisionally named golgin-95 and the SY2/SY10 protein was name d golgin-160. The deduced amino acid sequence of the cDNA clone of SY2 and SY11 represented 58.7- and 70-kD proteins of 568 and 620 amino ac ids. The in vitro translation products of SY2 and SY11 cDNAs migrated in SDS-PAGE at 65 and 95 kD, respectively. The in vitro translated pro teins were immunoprecipitated by human anti-Golgi serum or immune rabb it serum, but not by normal human serum or preimmune rabbit serum. Fea tures of the cDNA suggested that SY11 was a full-length clone encoding golgin-95 but SY2 and SY10 together encoded a partial sequence of gol gin-160. Analysis of the SY11 recombinant protein identified a leucine zipper spanning positions 419-455, a glutamic acid-rich tract spannin g positions 322-333, and a proline-rich tract spanning positions 67-73 . A search of the SwissProt data bank indicated sequence similarity of SY11 to human restin, the heavy chain of kinesin, and the heavy chain of myosin. SY2 shared sequence similarity with the heavy chain of myo sin, the USO1 transport protein from yeast, and the 150-kD cytoplasmic dynein-associated polypeptide. Sequence analysis demonstrated that go lgin-95 and golgin-160 share 43% sequence similarity and, therefore, m ay be functionally related proteins.