There has been general acceptance that only one type of androgen receptor (AR) exists in an individual. This contrasts with other members of the nuclear receptor superfamily where multiple forms have been reported (e.g. estrogen receptor ␣/␤, thyroid hormone receptor ␣/␤, etc.). We have previously identified 11-ketotestosterone (a potent androgen in teleosts) as the spermatogenesis-inducing hormone of the Japanese eel and have cloned its receptor (eAR1) cDNA from eel testis. Here we report on the cloning of a cDNA encoding a second type of AR (eAR2) from the eel testis and the functional characterization of the encoded protein. This cDNA contains a complete open reading frame encoding 797 amino acid residues. The amino acid sequence of eAR2 shows high homology with other ARs, including eAR1, in the DNAbinding (98 -88%) and ligand-binding (59 -85%) domains, whereas the other domains show low homology (<35%). In transient transfection assays of mammalian cells, the eAR2 protein displayed androgen-dependent activation of transcription from the androgen-responsive murine mammary tumor virus promoter. Tissue distribution of its mRNA was different from that of eAR1. We conclude that eAR2 is a novel AR in the eel, which we suggest should be named eel AR␤ to distinguish it from eAR1 (eAR␣).

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A cDNA encoding a nuclear 17K K,20L L-dihydroxy-4-pregnen-3-one (17K K,20L L-DP, spermiation-inducing hormone in fish) receptor (DPR) was, for the first time, isolated from an eel testis cDNA library. The amino acid sequence of DPR shows high homology with those of human and chicken progesterone receptors. The affinity of the bacterial recombinant DPR ligand binding domain protein for 17K K,20L L-DP is higher than that of progesterone. In transfection experiments using COS7 cells, the DPR showed progestin-dependent activation of transcription. 17K K,20L L-DP was the most effective activator of transcription. These results indicate that the cDNA encodes a functional eel DPR, and show that 17K K,20L L-DP has a nuclear receptormediated action in eel testes.z 2000 Federation of European Biochemical Societies.

The Z-scheme process in chlorophyll-based natural photosynthesis shows the pathway of photoinduced electron transport from photosystem II (PSII) to photosystem I (PSI) through an electron transfer chain. Inspired by the interesting Z-scheme of oxygenic photosynthesis, we imitated the dual photosynthesis systems into biosolar cells (BSCs). The device structure fabricated here is ITO/ZnO/Chl-A/Chl-D1, -D2, -D3, or -D4 (Chl-Ds)/MoO 3 /Ag. Due to higher HOMO/LUMO energy levels of Chl-A than those of Chl-Ds, the sublayer Chl-A corresponds to PSI, and the upper layer Chl-Ds are equivalent to PSII, leading to double photoexcited electron transfer from Chl-Ds to Chl-A. The energy alignment of the photoactive layers here is in conflict with the traditional comprehension of photovoltaic devices. Interestingly, such an uncommon device can still work well. A power conversion efficiency of 1.30% was reached based on the Chl-A/Chl-D4 device under standard AM1.5 illumination.

A cDNA encoding a second type of a progestogen receptor (ePR2) was isolated from the same library as we had previously cloned a functional PR (ePR1) in eel testis. The amino acid sequence of the ePR2 shows low homology with ePR1 (34%), but both PRs showed progestogen-dependent transactivation in transfection experiment. Tissue distribution of ePR2 mRNA was clearly different from that of ePR1. Protein interaction between two PRs was demonstrated in vitro by a glutathione S-transferase pull-down assay. These results indicate that ePR2 is also a functional PR. This is the first isolation of two different functional PR molecules from a vertebrate. ß