Abstract
Photosystem II (PSII) contains different extrinsic proteins among different organisms. Recently, Enami et al. succeeded in the preparation of PSII particles having high oxygen-evolving activity from a marine diatom Chaetoceros gracilis and found that the diatom PSII particles contained five extrinsic proteins, PsbO, PsbQ', PsbV, hypothetical protein and PsbU. In this study, we cloned and sequenced the genes encoding these five extrinsic proteins. Full-lengths of psbO, psbQ', hypothetical protein, and psbU cDNAs were isolated by degenerate RT-PCR and RLM-RACE. On the other hand, DNA fragment containing psbV gene was isolated using a combination of degenerate RT-PCR and inverse PCR. The results show that the former genes are encoded in the nuclear genome. After sequencing the genes, we found that all of the five extrinsic proteins have typical features for thylakoid transfer peptides. This suggests that the hypothetical protein is also one of the luminal extrinsic proteins functioning in oxygen evolution.
