Functional characterization and substrate specificity of a novel gene encoding zinc finger-like protein, ZfLp, in Xenopus laevis oocytes

In the present study, we isolated and determined the pharmacological characteristics of a novel gene encoding the zinc finger-like protein (ZfLp). The isolated cDNA consisted of 1,581 base pairs that encoded a 526-amino acid protein. The amino acid sequence of ZfLp is 96% identical to that of zinc finger protein 415 isoform 5 (ZNF415-5). Reverse-transcription (RT)-polymerase chain reaction (PCR) analysis revealed that the ZfLp mRNA is expressed in the breast, lung, stomach, small intestine colon and ovary, but not in the liver. When expressed in Xenopus laevis oocytes, ZfLp mediated the high affinity transport of [H-3]paclitaxel (taxol) in a sodium-independent manner (K-m = 336.7 +/- 190.0 nM). The uptake of [H-3]paclitaxel (taxol) by ZfLp was trans-stimulated by glutarate and glutathione (GSH). A cis-inhibition experiment revealed that ZfLp-mediated transport of [H-3]paclitaxel (taxol) is inhibited by several organic solutes specifically clotrimazole. Using several clotrimazole derivatives, we found that N-benzylimidazole would be a minimum unit for producing the inhibition of ZfLp-mediated drug uptake. Our results may provide insights into the novel role of soluble protein, such as ZNF, in the human body. Our results, therefore, would be expected to facilitate research on the novel role of ZNFs and on the discovery of novel drugs for targeting ZNF-related proteins such as ZfLp.