Widespread expression of a new putative hormone extrusion pump: NG-TRA transporter protein in human and rat tissue

In 1991 Becker and co-workers isolated a new ATP-dependent transporter from a neuroblastomaXglioma-hybrid-cell line, called NG-TRA. This protein was proposed to represent a hormone extrusion pump. To gain further insight into its significance we studied the expression of NG-TRA in human and rat tissues and compared the nucleotide sequences derived from both species using reverse transcription PCR, subcloning and nucleotide sequencing. A 97% sequence homology was found between the original and the human subcloned fragments, derived from thyroid and colon carcinoma tissue, while the rat subcloned fragments, derived from brain cortex and heart muscle, showed a 25 amino acid deletion at the 3'end compared with both the original and human subclones. Expression of NG-TRA at the mRNA level was found in all tissues studied except blood and fat tissue, and additionally rat lung tissue. We conclude that NG-TRA is a widely expressed protein consistent with a general function in diverse species.