title: Identification of two new members, XPLAC and XTES, of the XK family.
abstract: XK, a putative membrane transporter, is a component of the XK/Kell complex of the Kell blood group system. XK's substrate is unknown but absence of the protein, as occurs in the McLeod phenotype, is associated with red cell acanthocytosis and late onset central nervous system and neuromuscular abnormalities known as the McLeod syndrome. We have cloned two cDNAs, XPLAC (GenBank accession no. AY589511) and XTES (GenBank accession no. AY989815), which are closely related to XK and define them together as the XK family. XPLAC has a 2.9 kb cDNA that encodes 462 amino acids and XTES has a 1.6 kb cDNA coding 459 amino acids. The predicted molecular weights are 53.6 kDa for XPLAC and 53.4 kDa for XTES, which are similar to that of XK, which is 50.9 kDa. Unlike XK which is ubiquitously expressed XPLAC is expressed mostly in placenta and adrenal gland while XTES is exclusively expressed in primate testis. XPLAC has 37% and XTES has 31% amino acid identity with XK protein and they are predicted to have a similar topology to XK. XPLAC, like XK, has 3 exons and is located on X chromosome at q22.1, while XTES has 4 exons and is located at 22q11.1. Phylogenetic analysis shows that there are at least 5 additional vertebrate genes that are evolutionarily distantly related to the XK family. A domain with consensus sequences (ced-8 domain) for the extended family is described.
authors.affiliation: The Lindsley F. Kimball Research Institute of the New York Blood Center, 310 East 67th Street, New York, NY 10021, USA.
authors.forename: Giulia
authors.initials: G
authors.lastname: Calenda
authors.forename: Jianbin
authors.initials: J
authors.lastname: Peng
authors.forename: Colvin M
authors.initials: CM
authors.lastname: Redman
authors.forename: Quan
authors.initials: Q
authors.lastname: Sha
authors.forename: Xu
authors.initials: X
authors.lastname: Wu
authors.forename: Soohee
authors.initials: S
authors.lastname: Lee
mesh_terms: D000050:Acanthocytes / Q000378:metabolism / Q000473:pathology; D000311:Adrenal Glands / Q000166:cytology / Q000378:metabolism; D000595:Amino Acid Sequence; D000743:Anemia, Hemolytic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D002892:Chromosomes, Human, Pair 22 / Q000235:genetics*; D041321:Chromosomes, Human, X / Q000235:genetics*; D003001:Cloning, Molecular / Q000379:methods; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D007626:Kell Blood-Group System / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D009468:Neuromuscular Diseases / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009928:Organ Specificity / Q000502:physiology; D010802:Phylogeny; D010920:Placenta / Q000166:cytology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013737:Testis / Q000166:cytology / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D007626:Kell Blood-Group System; D026901:Membrane Transport Proteins; C510504:XKR3 protein, human; C510503:XKRX protein, human