MOLECULAR-BASIS FOR ERYTHROCYTE LE(A-SECRETOR PHENOTYPES - EXPRESSIONOF A FUT2 SECRETOR ALLELE WITH AN A-]T MUTATION AT NUCLEOTIDE-385 CORRELATES WITH REDUCED ALPHA(1,2)FUCOSYLTRANSFERASE ACTIVITY(B+) AND SALIVARY ABH PARTIAL)

The Se-wA385T mutation of the FUT2 gene was found to correlate with bo th the erthrocyte Le(a+b+) andior salivary ABH partial-secretor phenot ypes of Polynesians. Constructs with FUT1 and FUT2 wild type genes, an d the FUT2 Se-wA385T, Se-G428A and se(C571T) mutated alleles, were clo ned into pcDNAI, and expressed in COS-7 cells. COS-7 cells transfected with the Se-wA385T allele had weak, but detectable, alpha(1,2)fucosyl transferase activity, with an acceptor substrate pattern similar to th e wild type FUT2 gene. Comparative kinetic studies from cell extracts with mutated Se-wA385T and wild type FUT2 alleles gave similar K-m val ues, but less enzyme activity was present in cells transfected with Se -wA385T (V-max 230 pmol h(-1) mg(-1)), as compared to those transfecte d with FUT2.(V-max 1030 pmol h(-1) mg(-1)), suggesting that the mutate d enzyme is more unstable. These results confirm that the molecular ba sis for the erythrocyte Le(a+b+), and the associated ABH salivary part ial-secretor phenotype, is anamino acid change of Ile129 --> Phe in th e secretor alpha(1,2)fucosyltransferase.