Seccia Roberta, De Santis Silvia, Di Noia Maria A, Palmieri Ferdinando, Miniero Daniela V, Marmo Raffaele, Paradies Eleonora, Santoro Antonella, Pierri Ciro L, Palmieri Luigi, Marobbio Carlo M T, Vozza Angelo
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy.
CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), 70125 Bari, Italy.
J Fungi (Basel). 2022 Jul 29;8(8):795. doi: 10.3390/jof8080795.
The yeast mitochondrial transport of GTP and GDP is mediated by Ggc1p, a member of the mitochondrial carrier family. The physiological role of Ggc1p in is probably to transport GTP into mitochondria in exchange for GDP generated in the matrix. Δ cells exhibit lower levels of GTP and increased levels of GDP in mitochondria, are unable to grow on nonfermentable substrates and lose mtDNA. Because in yeast, succinyl-CoA ligase produces ATP instead of GTP, and the mitochondrial nucleoside diphosphate kinase is localized in the intermembrane space, Ggc1p is the only supplier of mitochondrial GTP required for the maturation of proteins containing Fe-S clusters, such as aconitase [4Fe-4S] and ferredoxin [2Fe-2S]. In this work, it was demonstrated that citrate is a regulator of purified and reconstituted Ggc1p by trans-activating unidirectional transport of GTP across the proteoliposomal membrane. It was also shown that the binding site of Ggc1p for citrate is different from the binding site for the substrate GTP. It is proposed that the citrate-induced GTP uniport (CIGU) mediated by Ggc1p is involved in the homeostasis of the guanine nucleotide pool in the mitochondrial matrix.
GTP和GDP的酵母线粒体转运由线粒体载体家族成员Ggc1p介导。Ggc1p在其中的生理作用可能是将GTP转运到线粒体中，以交换基质中产生的GDP。Δ细胞线粒体中的GTP水平较低，GDP水平升高，无法在非发酵底物上生长并丢失线粒体DNA。由于在酵母中，琥珀酰辅酶A连接酶产生ATP而非GTP，且线粒体核苷二磷酸激酶定位于膜间隙，Ggc1p是含Fe-S簇的蛋白质（如乌头酸酶[4Fe-4S]和铁氧化还原蛋白[2Fe-2S]）成熟所需线粒体GTP的唯一供应者。在这项研究中，已证明柠檬酸盐通过反式激活GTP跨蛋白脂质体膜的单向转运，成为纯化和重组Ggc1p的调节剂。还表明Ggc1p与柠檬酸盐的结合位点不同于与底物GTP的结合位点。有人提出，由Ggc1p介导的柠檬酸盐诱导的GTP单向转运（CIGU）参与线粒体基质中鸟嘌呤核苷酸池的稳态。
