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Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins

Mitochondrial carriers, which transport metabolites, nucleotides, and cofactors across the mitochondrial inner membrane, have six transmembrane α-helices enclosing a translocation pore with a central substrate binding site whose access is controlled by a cytoplasmic and a matrix gate (M-gate). The s...

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Autores principales: Miniero, Daniela Valeria, Monné, Magnus, Di Noia, Maria Antonietta, Palmieri, Luigi, Palmieri, Ferdinando
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9104175/
https://www.ncbi.nlm.nih.gov/pubmed/35563451
http://dx.doi.org/10.3390/ijms23095060
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author Miniero, Daniela Valeria
Monné, Magnus
Di Noia, Maria Antonietta
Palmieri, Luigi
Palmieri, Ferdinando
author_facet Miniero, Daniela Valeria
Monné, Magnus
Di Noia, Maria Antonietta
Palmieri, Luigi
Palmieri, Ferdinando
author_sort Miniero, Daniela Valeria
collection PubMed
description Mitochondrial carriers, which transport metabolites, nucleotides, and cofactors across the mitochondrial inner membrane, have six transmembrane α-helices enclosing a translocation pore with a central substrate binding site whose access is controlled by a cytoplasmic and a matrix gate (M-gate). The salt bridges formed by the three PX[DE]XX[RK] motifs located on the odd-numbered transmembrane α-helices greatly contribute to closing the M-gate. We have measured the transport rates of cysteine mutants of the charged residue positions in the PX[DE]XX[RK] motifs of the bovine oxoglutarate carrier, the yeast GTP/GDP carrier, and the yeast NAD(+) transporter, which all lack one of these charged residues. Most single substitutions, including those of the non-charged and unpaired charged residues, completely inactivated transport. Double mutations of charged pairs showed that all three carriers contain salt bridges non-essential for activity. Two double substitutions of these non-essential charge pairs exhibited higher transport rates than their corresponding single mutants, whereas swapping the charged residues in these positions did not increase activity. The results demonstrate that some of the residues in the charged residue positions of the PX[DE]XX[KR] motifs are important for reasons other than forming salt bridges, probably for playing specific roles related to the substrate interaction-mediated conformational changes leading to the M-gate opening/closing.
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spelling pubmed-91041752022-05-14 Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins Miniero, Daniela Valeria Monné, Magnus Di Noia, Maria Antonietta Palmieri, Luigi Palmieri, Ferdinando Int J Mol Sci Article Mitochondrial carriers, which transport metabolites, nucleotides, and cofactors across the mitochondrial inner membrane, have six transmembrane α-helices enclosing a translocation pore with a central substrate binding site whose access is controlled by a cytoplasmic and a matrix gate (M-gate). The salt bridges formed by the three PX[DE]XX[RK] motifs located on the odd-numbered transmembrane α-helices greatly contribute to closing the M-gate. We have measured the transport rates of cysteine mutants of the charged residue positions in the PX[DE]XX[RK] motifs of the bovine oxoglutarate carrier, the yeast GTP/GDP carrier, and the yeast NAD(+) transporter, which all lack one of these charged residues. Most single substitutions, including those of the non-charged and unpaired charged residues, completely inactivated transport. Double mutations of charged pairs showed that all three carriers contain salt bridges non-essential for activity. Two double substitutions of these non-essential charge pairs exhibited higher transport rates than their corresponding single mutants, whereas swapping the charged residues in these positions did not increase activity. The results demonstrate that some of the residues in the charged residue positions of the PX[DE]XX[KR] motifs are important for reasons other than forming salt bridges, probably for playing specific roles related to the substrate interaction-mediated conformational changes leading to the M-gate opening/closing. MDPI 2022-05-02 /pmc/articles/PMC9104175/ /pubmed/35563451 http://dx.doi.org/10.3390/ijms23095060 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Miniero, Daniela Valeria
Monné, Magnus
Di Noia, Maria Antonietta
Palmieri, Luigi
Palmieri, Ferdinando
Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins
title Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins
title_full Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins
title_fullStr Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins
title_full_unstemmed Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins
title_short Evidence for Non-Essential Salt Bridges in the M-Gates of Mitochondrial Carrier Proteins
title_sort evidence for non-essential salt bridges in the m-gates of mitochondrial carrier proteins
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9104175/
https://www.ncbi.nlm.nih.gov/pubmed/35563451
http://dx.doi.org/10.3390/ijms23095060
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