Isolation and Chromosomal Mapping of a Novel ATP-Binding Cassette Transporter Conserved in Mouse and Human (original) (raw)

The sequencing of the longest clone (2684 bp-Gen-We report here on the identification and genomic Bank Accession No. U43892) by systematic subcloning mapping of a novel member of the family of the ATPin plasmid vectors and oligonucleotide walk was carbinding cassette (ABC) transporters, ABC7, conserved ried out on both strands by the Sanger dideoxy chain in mouse and in humans. The ABC7 gene encodes a termination method on double-stranded templates protein with the typical features of half-transporters, (U.S. Biochemicals; Sequenase kits). A single open such as those involved in translocation of antigenic reading frame starting from ATG 196 was detected by peptides or in peroxisomal disorders. ABC7 shows a standard analytical tools. However, since no in-frame ubiquitous expression pattern and maps to the X chrostop codon could be found upstream to ATG 196, we mosome both in mouse and in humans. The high secannot unambiguously conclude that the whole coding quence similarity to those of two yeast half-transportregion has been identified. Provided that this ATG eners supports once again the extreme evolutionary concodes the amino-terminal methionine, a protein of 629 servation of this family of proteins. ᭧ 1997 Academic Press amino acids (bp 196-2085) in length will be produced upon translation. The hydrophobicity analysis of the conceptual protein sequence was carried out accord-The family of ATP-binding cassette (ABC) transingly to Kyte-Doolittle and Eisenberg hydrophobicity porters is extremely conserved across evolution from algorithms, and it revealed the presence of six putative bacteria to humans, and is the largest protein family transmembrane spanners in close succession in the Nknown so far, since it comprises more than 150 memterminal segment. This membrane-anchoring domain bers (4). Relatively few mammalian members have is followed by a canonical ATP-binding cassette, therebeen identified in the recent years, but most of them fore allowing us to classify ABC7 as a typical halfare at the molecular basis of clinically relevant phetransporter (4). notypes. We reported recently on the identification A search of sequence databases using the BLAST of several novel transporters conserved in mouse and program (2) revealed two yeast ABC transporters in humans, via a strategy based on cDNA amplificacloser to ABC7 than to the other members of the family, tion with degenerate primers targeted to diagnostic since the homology extends beyond the most conserved consensus sequences (7, 8,. region of the ABC domain. HTM1_SCHPO, expressed The isolation and partial characterization of an addion the vacuolar membrane of Schizosaccharomyces tional novel member of this family, named ABC7, are pombe and involved in resistance to heavy metals reported here. The ABC7-encoding sequence was first (10,11), displays an identity to ABC7 of 37.2% on a 490isolated from mouse macrophage cDNA by the already nt segment. ATM1_YEAST, a mitochondrial transdescribed procedure as an amplification product of 340 porter required for yeast growth , shows an identity bp spanning the ATP-binding cassette (12). The sets of of 49.3% over 600 residues . The homology bedegenerate primers were as described in Ref. 12. The tween ABC7 and both these transporters is more eviassessment of its bona fide belonging to a transcript dent in the 200-aa-long region of the ABC domain (52% for a novel ABC transporter led to the screening of a identity in both cases), whereas the C-and N-terminal cDNA library derived from the same P388D1 cell line parts are more divergent. Several clusters of conserved and the isolation of 17 overlapping l clones.