| Research Abstract |
TAP-like (TAPL) is a half type ATP-binding cassette (ABC) transporter with sequence similarity to transporter associated with antigen processing (TAP)1 and TAP2, and is highly conserved in mammals [Kobayashi, A., et al. (2000) J. Biochem. 128, 711-718]. Tissue distribution of TAP family (TAP1, TAP2 and TAPL) in rat was investigated by semi-quantitative Reverse transcriptase polymerase chain reaction (RT-PCR). In young male rat, higher amounts of TAPL mRNA were detected in brain and testis rather than in thymus and intestine. On the other hand, both TAP1 and TAP2 mRNAs were expressed higher in thymus. Furthermore, the expression level of TAP1 in intestine and that of TAP2 in brain and testis were also high. Analysis of rat TAPL cDNAs demonstrated that that the carboxyl terminal sequence of ATP binding region was heterogeneous. At least four different isoforms (C-I, II, III and IV) could be produced by alternative splicing of mRNA, as was confirmed by genomic data search. Both C-III and C-IV types had shorter carboxyl terminal sequences, and the C-III had the shortest. Differential expression of them in brain and testis were observed. The functional heterogeneity of the carboxyl terminal splicing variants of TAPL is expected.
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