Molecular cloning of a fourth member of a human alpha (1,3)fucosyltransferase gene family. Multiple homologous sequences that determine expression of the Lewis x, sialyl Lewis x, and difucosyl sialyl Lewis x epitopes. We and others have previously described the isolation of three human alpha (1,3)fucosyltransferase genes which form the basis of a nascent glycosyltransferase ge