The substrate specificity of mitochondrial carriers: mutagenesis revisited.

TitleThe substrate specificity of mitochondrial carriers: mutagenesis revisited.
Publication TypeJournal Article
Year of Publication2013
AuthorsMonné, M, Palmieri, F, Kunji, ERS
JournalMol Membr Biol
Date Published2013 Mar
KeywordsBinding Sites, Biological Transport, Mitochondria, Mitochondrial Proteins, Mutagenesis, Protein Structure, Secondary, Substrate Specificity

Mitochondrial carriers transport inorganic ions, nucleotides, amino acids, keto acids and cofactors across the mitochondrial inner membrane. Structurally they consist of three domains, each containing two transmembrane α-helices linked by a short α-helix and loop. The substrate binds to three major contact points in the central cavity. The class of substrate (e.g., adenine nucleotides) is determined by contact point II on transmembrane α-helix H4 and the type of substrate within the class (e.g., ADP, coenzyme A) by contact point I in H2, whereas contact point III on H6 is most usually a positively charged residue, irrespective of the type or class. Two salt bridge networks, consisting of conserved and symmetric residues, are located on the matrix and cytoplasmic side of the cavity. These residues are part of the gates that are involved in opening and closing of the carrier during the transport cycle, exposing the central substrate binding site to either side of the membrane in an alternating way. Here we revisit the plethora of mutagenesis data that have been collected over the last two decades to see if the residues in the proposed binding site and salt bridge networks are indeed important for function. The analysis shows that the major contact points of the substrate binding site are indeed crucial for function and in defining the specificity. The matrix salt bridge network is more critical for function than the cytoplasmic salt bridge network in agreement with its central position, but neither is likely to be involved in substrate recognition directly.

Alternate JournalMol. Membr. Biol.
Citation Key10.3109/09687688.2012.737936
PubMed ID23121155
Grant ListMC_U105663139 / / Medical Research Council / United Kingdom