MOLECULAR-CLONING AND EXPRESSION OF 2 TYPES OF RABBIT BETA-GALACTOSIDE ALPHA-1,2-FUCOSYL-TRANSFERASE

Two DNA clones encoding rabbit beta-galactoside alpha 1,2-fucosyltrans ferase (RFT-I and RFT-II) have been isolated from a rabbit genomic DNA library. The DNA sequences revealed open reading frames coding for 37 3 (RFT-I) and 354 (RFT-II) amino acids, respectively. The deduced amin o acid sequences of RFT-I and RFT-II showed 56% identity with each oth er, and that of RFT-I showed 80% identity with that of human H blood t ype alpha 1,2-fucosyltransferase. Northern blot analysis of embryo and adult rabbit tissues revealed that the RFT-I gene was expressed in ad ult brain, and that the RFT-II gene was expressed in salivary and lact ating mammary glands. The identities of these enzymes were confirmed b y constructing recombinant fucosyltransferases in which the N-terminal part including the cytoplasmic tail and signal anchor domain was repl aced with the immunoglobulin signal peptide sequence. RFT-I expressed in COS-7 cells exhibited similar transferase activity to that of human H blood type alpha 1,2-fucosyltransferase. RFT-II expressed in COS-7 cells showed higher affinity for type 1 (Gal beta 1,3GlcNAc) and type 3 (Gal beta 1,3GalNAc) acceptors than type 2 (Gal beta 1,4GlcNAc) ones , which suggested that RFT-II was a putative secretor-type alpha 1,2-f ucosyltransferase.