Structural characterization of the transmembrane segments of the mitochondrial oxoglutarate carrier (OGC)by NMR spectroscopy

Abstract. The oxoglutarate carrier (OGC) is a member of the mitochondrial carrier protein superfamily, which includes the ADP/ATP carrier and other functionally characterized members, and exchanges cytosolic malate for 2-oxoglutarate from the mitochondrial matrix. By means of CD and NMR spectroscopy, we previously characterized four synthetic peptides containing transmembrane segments (TMSs) I, II, V and VI of the OGC, respectively, in TFE/water mixtures and SDS micelles. Here, we present data on the remaining transmembrane segments of OGC obtained by performing CD and NMR studies on peptides corresponding to TMS-III and TMS-IV. In TFE/water, alpha-helical structures were found for these peptides in the L121-R146 and T187-S201 regions, respectively. We also evaluated the compatibility between the helical structures of our peptides and a homology model of the OGC based on the available X-ray structure of the ATP/ADP carrier. Key words: NMR; mitochondrial carriers; mitochondrial oxoglutarate carrier; structure; transmembrane segments.