They localize to the cytosol as well as the mitochondrion and peroxisome. Galectin-3 is expressed in the nucleus, cytoplasm, mitochondrion, cell surface, and extracellular space. The latter exists as an isozyme located in both the mitochondrion and the cytosol. The HMGCL gene encodes a 34.5-kDa protein that is localized to the mitochondrion and peroxisome. In eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion. They are found predominantly in mitochondrion and peroxisomes. Oxidative phosphorylation in the eukaryotic mitochondrion is the best-understood example of this process. Pyruvate is then decarboxylated to form acetyl-CoA in the mitochondrion. A single mitochondrion is often found in unicellular organisms. For example, oxaloacetate is formed by malate dehydrogenase within the mitochondrion. This occurs via the conversion of pyruvate into acetyl-CoA in the mitochondrion. For example, if oligomycin inhibits ATP synthase, protons cannot pass back into the mitochondrion. For example, a single mitochondrion may divide synchronously with the nucleus. The oxaloacetate is returned to the mitochondrion as malate. It contains about 2/3 of the total proteins in a mitochondrion.