HIGH PRESSURE COOLING OF CYTOCHROME C OXIDASE

点击翻译按钮获取中文摘要

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cytochrome c oxidase (CcO) is the terminal enzyme in the electron transfer chain in eukaryotes and many bacteria. It provides the final electron sink by accepting electrons from cytochrome c and passing them on to oxygen to form water. Over the past decade, several x-ray crystal structures of aa3-type oxidases have been determined from bovine heart mitochondria and bacteria. This new wealth of structural information, combined with spectroscopic and site-directed mutagenesis studies, has greatly enhanced our understanding of the structure/function aspects of this multisubunit membrane protein complex. However, the mechanism of vectorial translocation of protons and its coupling to electron transfer and oxygen reduction is yet to be solved. Although we now have crystals diffracting to 2.35 A resolution, a key question is the arrangement of water molecules in the structure that form proton transfer pathways, as well as changes in water arrangement in mutant forms, hence the need for higher quality diffraction data. It was reported that protein crystals cryo-cooled at high pressure (200Mpa) diffract excellently even without any penetrating cryoprotectants. So in this experiment, cytochrome c oxidase crystals will be handled by high pressure cooling method and high quality data sets will be collected.