Truncation of subunit ND2 disrupts the threefold symmetry of the antiporter‐like subunits in complex I from higher metazoans

Birrell, James A.; Hirst, Judy

doi:10.1016/j.febslet.2010.09.017

Cited by 39 publications

(34 citation statements)

References 39 publications

(76 reference statements)

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“…In this case, NUXM can be assigned to the two TMHs that are specific to Y. lipolytica (Fig. S3), consistent with the composition of Y. lipolytica subcomplex Iδ (17), and with the position of these two TMHs adjacent to the three N-terminal TMHs of ND2 that are also absent from B. taurus (18).…”

Section: Resultssupporting

confidence: 74%

Structure of subcomplex Iβ of mammalian respiratory complex I leads to new supernumerary subunit assignments

Zhu

King

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Mitochondrial complex I (proton-pumping NADH:ubiquinone oxidoreductase) is an essential respiratory enzyme. Mammalian complex I contains 45 subunits: 14 conserved "core" subunits and 31 "supernumerary" subunits. The structure of Bos taurus complex I, determined to 5-Å resolution by electron cryomicroscopy, described the structure of the mammalian core enzyme and allowed the assignment of 14 supernumerary subunits. Here, we describe the 6.8-Å resolution X-ray crystallography structure of subcomplex Iβ, a large portion of the membrane domain of B. taurus complex I that contains two core subunits and a cohort of supernumerary subunits. By comparing the structures and composition of subcomplex Iβ and complex I, supported by comparisons with Yarrowia lipolytica complex I, we propose assignments for eight further supernumerary subunits in the structure. Our new assignments include two CHCH-domain containing subunits that contain disulfide bridges between CX 9 C motifs; they are processed by the Mia40 oxidative-folding pathway in the intermembrane space and probably stabilize the membrane domain. We also assign subunit B22, an LYR protein, to the matrix face of the membrane domain. We reveal that subunit B22 anchors an acyl carrier protein (ACP) to the complex, replicating the LYR protein-ACP structural module that was identified previously in the hydrophilic domain. Thus, we significantly extend knowledge of how the mammalian supernumerary subunits are arranged around the core enzyme, and provide insights into their roles in biogenesis and regulation.CHCH domain | electron transport chain | LYR protein | mitochondria | NADH:ubiquinone oxidoreductase I n mammalian mitochondria, respiratory complex I (NADH: ubiquinone oxidoreductase) (1, 2) contains 45 subunits with a combined mass of 1 MDa (3-6). Fourteen core subunits, conserved from bacteria to humans, constitute the minimal complex I and catalyze the energy transducing reaction: NADH oxidation and ubiquinone reduction coupled to proton translocation across the inner membrane. Complex I is thus critical for mammalian metabolism: it oxidizes the NADH generated by the tricarboxylic acid cycle and β-oxidation, produces ubiquinol for the rest of the respiratory chain, and contributes to the proton-motive force that supports ATP synthesis and transport processes. Seven of the core subunits are hydrophilic proteins that are encoded in the nucleus and imported to mitochondria, and the other seven are hydrophobic, membrane-bound proteins (known as the ND subunits) that are encoded by the mitochondrial genome. These two sets of seven subunits form the two major domains of complex I, in the matrix and inner membrane, which confer its characteristic L shape.The protein composition of complex I from Bos taurus heart mitochondria has been characterized extensively, and is the blueprint for the human enzyme (3-6). In addition to the 14 core subunits it contains 31 supernumerary subunits (including two copies of the acyl-carrier protein, SDAP; ref. 2). Several supernumerary subunit...

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Section: Resultssupporting

confidence: 74%

Structure of subcomplex Iβ of mammalian respiratory complex I leads to new supernumerary subunit assignments

Zhu

King

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Observation of the same stoichiometry value for both a mammalian and a bacterial complex I suggests that it is widely conserved and not affected by the truncation of subunit ND2 in metazoans (47) or by the many supernumerary subunits of the eukaryotic complexes. However, among bacterial complexes I, the P. denitrificans enzyme is relatively similar to the mammalian one: P. denitrificans is an α-proteobacterium closely related to the protomitochondrion (25), and it uses ubiquinone as its electron acceptor.…”

Section: Discussionmentioning

confidence: 92%

Respiratory Complex I in Bos taurus and Paracoccus denitrificans Pumps Four Protons across the Membrane for Every NADH Oxidized

Jones

Blaza

Varghese

et al. 2017

Journal of Biological Chemistry

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Respiratory complex I couples electron transfer between NADH and ubiquinone to proton translocation across an energy-transducing membrane to support the proton-motive force that drives ATP synthesis. The proton-pumping stoichiometry of complex I (i.e. the number of protons pumped for each two electrons transferred) underpins all mechanistic proposals. However, it remains controversial and has not been determined for any of the bacterial enzymes that are exploited as model systems for the mammalian enzyme. Here, we describe a simple method for determining the proton-pumping stoichiometry of complex I in inverted membrane vesicles under steady-state ADP-phosphorylating conditions. Our method exploits the rate of ATP synthesis, driven by oxidation of NADH or succinate with different sections of the respiratory chain engaged in catalysis as a proxy for the rate of proton translocation and determines the stoichiometry of complex I by reference to the known stoichiometries of complexes III and IV. Using vesicles prepared from mammalian mitochondria (from Bos taurus) and from the bacterium Paracoccus denitrificans, we show that four protons are pumped for every two electrons transferred in both cases. By confirming the four-proton stoichiometry for mammalian complex I and, for the first time, demonstrating the same value for a bacterial complex, we establish the utility of P. denitrificans complex I as a model system for the mammalian enzyme. P. denitrificans is the first system described in which mutagenesis in any complex I core subunit may be combined with quantitative proton-pumping measurements for mechanistic studies.

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“…1). Previous bioinformatics analysis has revealed that all pre-bilaterian organisms contain a ‘long' ND2 sequence with three extra N-terminal TM helices, whereas all higher, bilaterian organisms only contain the ‘short' ND2 sequence3233 (Supplementary Fig. 2).…”

Section: Resultsmentioning

confidence: 99%

“…By contrast the ‘long' 14 TMD form is found in more primitive organisms, such as prokaryotes, with cnidarians encoding both ‘long' and ‘short' ND2 (ref. 32). The loss of these three TM helices in higher organisms does not appear to interfere with the electron transport chain function of ND2 and this ‘short' form is subsequently conserved in higher organisms32.…”

Section: Discussionmentioning

confidence: 99%

An evolutionary switch in ND2 enables Src kinase regulation of NMDA receptors

et al. 2017

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The non-receptor tyrosine kinase Src is a key signalling hub for upregulating the function of N-methyl D-aspartate receptors (NMDARs). Src is anchored within the NMDAR complex via NADH dehydrogenase subunit 2 (ND2), a mitochondrially encoded adaptor protein. The interacting regions between Src and ND2 have been broadly identified, but the interaction between ND2 and the NMDAR has remained elusive. Here we generate a homology model of ND2 and dock it onto the NMDAR via the transmembrane domain of GluN1. This interaction is enabled by the evolutionary loss of three helices in bilaterian ND2 proteins compared to their ancestral homologues. We experimentally validate our model and demonstrate that blocking this interaction with an ND2 fragment identified in our experimental studies prevents Src-mediated upregulation of NMDAR currents in neurons. Our findings establish the mode of interaction between an NMDAR accessory protein with one of the core subunits of the receptor.

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Truncation of subunit ND2 disrupts the threefold symmetry of the antiporter‐like subunits in complex I from higher metazoans

Cited by 39 publications

References 39 publications

Structure of subcomplex Iβ of mammalian respiratory complex I leads to new supernumerary subunit assignments

Structure of subcomplex Iβ of mammalian respiratory complex I leads to new supernumerary subunit assignments

Respiratory Complex I in Bos taurus and Paracoccus denitrificans Pumps Four Protons across the Membrane for Every NADH Oxidized

An evolutionary switch in ND2 enables Src kinase regulation of NMDA receptors

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