Evolution of Vertebrate Solute Carrier Family 9B Genes and Proteins (): Evidence for a Marsupial Origin for Testis Specific from an Ancestral Vertebrate Gene.

genes and proteins are members of the sodium/lithium hydrogen antiporter family which function as solute exchangers within cellular membranes of mammalian tissues. and amino acid sequences and structures and -like gene locations were examined using bioinformatic data from several vertebrate genome projects. Vertebrate sequences shared 56-98% identity as compared with ∼50% identities with mammalian sequences. Sequence alignments, key amino acid residues and conserved predicted transmembrane structures were also studied. Mammalian and genes usually contained 11 or 12 coding exons with differential tissue expression patterns: broad tissue distribution; and , being testis specific. Transcription factor binding sites and CpG islands within the human and gene promoters were identified. Phylogenetic analyses suggested that originated in an ancestral marsupial genome from a gene duplication event.