Structure of PIN-domain protein PH0500 from Pyrococcus horikoshii

The Pyrococcus horikoshii OT3 protein PH0500 is highly conserved within the Pyrococcus genus of hyperthermophilic archaea and shows low amino‐acid sequence similarity with a family of PIN‐domain proteins. The protein has been expressed, purified and crystallized in two crystal forms: PH0500‐I and PH0500‐­II. The structure was determined at 2.0 Å by the multiple anomalous dispersion method using a selenomethionyl derivative of crystal form PH0500‐I (PH0500‐I‐Se). The structure of PH0500‐I has been refined at 1.75 Å resolution to an R factor of 20.9% and the structure of PH0500‐II has been refined at 2.0 Å resolution to an R factor of 23.4%. In both crystal forms as well as in solution the molecule appears to be a dimer. Searches of the databases for protein‐fold similarities confirmed that the PH0500 protein is a PIN‐domain protein with possible exonuclease activity and involvement in DNA or RNA editing.