NUCLEOTIDE TRANSPORTATION BY A MITOCHONDRIAL CARRIER

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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. The hydrolysis of adenosine triphosphate (ATP) provides energy for numerous metabolic reactions in a cell. In eukaryotic cells, ATP is synthesized inside the mitochondria from adenosine diphosphate (ADP) and inorganic phosphate. The newly synthesized ATP is then exported to the cytoplasm to be consumed, while cytosolic ADP is imported to the mitochondria for ATP regeneration. The exchange of ADP and ATP across the mitochondrial membrane is mediated by the mitochondrial ADP/ATP carrier, a membrane protein which has been proposed to cycle between two conformationally distinct states, cytosolic-open (c-state) and matrix-open (m-state), thereby shuttling nucleotides across the inner mitochondrial membrane (http://www.ks.uiuc.edu/Research/AdpAtpCarrier/). The c-state of the carrier is the only structurally known state [1]. As a result, conformational changes of the carrier involved in an exchange cycle remained elusive.