Yokohama City University^* Mie University^**
○Hiroshi Hashimoto^* Shigeta Kawaguchi^* Naoki Shichijo^* Satoru Unzai^* Keishi Nakamura^** Toshiyuki Shimizu^* Yutaka Tamaru^** Mamoru Sato^*

The germ cell is the only cell descended to the next generation. It has the totipotency that invents all soma and germ cells again. In general, germ cell precursor move to conceptacle and then the precursor differentiates to germ cell. It is, however, unclear about the formation mechanism of germ cell, translational control plays crucial role to express proteins in differentiation of germ cell, because transcription is absent in later stages of germ cell differentiation and does not resume until some time in early development. Nanos and Pumilio proteins are translational repressor and they play significant role in formation of germ cell. They bind nanos response element (NRE) in 3'-UTR of mRNA and repress translation of the target mRNA. Crystal structures of Pumilio and the complex with NRE were determined, previously. Although these structures reveal interaction between Pumilio and NRE, no structural insight of Nanos is known. In this work, we determined the crystal structure of Nanos. The structure of Nanos will provide a clue to reveal the mechanism of translational control by Nanos and Pumilio.
Crystals of Nanos were obtained by hanging drop vapor diffusion method using polyethylene glycol as a precipitant. Nanos is Zinc finger protein and contains two CCHC motifs. Thus, the crystal structure of Nanos was determined by single wavelength anomalous dispersion (SAD) technique using zinc atom. Initial phases were determined with the program SOLVE and were improved with the program RESOLVE. The initial model was build by the program O. The structure refinement is now in progress using the programs CNS and REFMAC.