Journal of Biological Chemistry
Volume 272, Issue 35, 29 August 1997, Pages 21994-21998
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CARBOHYDRATES, LIPIDS, AND OTHER NATURAL PRODUCTS
Significance of Individual Point Mutations, T202C and C314T, in the Human Lewis (FUT3) Gene for Expression of Lewis Antigens by the Human α(1,3/1,4)-Fucosyltransferase, Fuc-TIII*

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The Lewis α(1,3/1,4)-fucosyltransferase, Fuc-TIII, encoded by theFUT3 gene is responsible for the final synthesis of Lea and Leb antigens. Various point mutations have been described explaining the Lewis negative phenotype, Le(a−b−), on erythrocytes and secretions. Two of these, T202C and C314T originally described in a Swedish population, have not been found as single isolated point mutations so far. To define the relative contribution of each of these two mutations to the Lewis negative phenotype, we cloned and made chimeric FUT3 constructs separating the T202C mutation responsible for the amino acid change Trp68 → Arg, from the C314T mutation leading to the Thr105 → Met shift. COS-7 cells were transfected and the expression of Fuc-TIII enzyme activity and the presence of Lewis antigens were determined. There was no decrease in enzyme activity nor of immunofluorescence staining on cells transfected with the construct containing the isolated C314T mutation compared with cells transfected with a wild type FUT3 allele control. No enzyme activity nor immunoreactivity for Lewis antigens was detected inFUT3 constructs containing both mutations in combination. The T202C mutation alone decreased the enzyme activity to less than 1% of the activity of the wild type FUT3 allele. These results demonstrate, that the Trp68 → Arg substitution in human Fuc-TIII is the capital amino acid change responsible for the appearance of the Le(a−b−) phenotype on human erythrocytes in individuals homozygous for both the T202C and C314T mutations.

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*

The work was supported by Grants 8266 and K96-03RM-11718 from the Swedish Medical Research Council, grants from the Medical Faculty of Göteborg University, the Swedish Society for Medical Research, the Göteborg Medical Society, the Wilhelm and Martina Lundgren's Research Foundation, Grant 9514111 “Action Concertée Coordonnée des Sciences du Vivant” (ACCSV14) from the “Ministère de l'Education Nationale de l'Enseignement Supérieur et de la Recherche” (MENESR, France), and Immunology concerted action 3026PL950004 of the Biotechnology program from the European Union (EU).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

FUT1 to FUT7 are the Genome Data Base (GDB) registered names of the cloned human fucosyltransferase genes, accessible in the EMBL/GenBank data libraries under accession numbers: M35531, U17894,X53578, M58596/M58597/S65161/M65030, M81485, L01698/M98825, andX78031/U08112/U11282.