Function and Structure of Complex II of the Respiratory Chain

Abstract

Complex II is the only membrane-bound component of the Krebs cycle and in addition functions as a member of the electron transport chain in mitochondria and in many bacteria. A recent X-ray structural solution of members of the complex II family of proteins has provided important insights into their function. One feature of the complex II structures is a linear electron transport chain that extends from the flavin and iron-sulfur redox cofactors in the membrane extrinsic domain to the quinone and b heme cofactors in the membrane domain. Exciting recent developments in relation to disease in humans and the formation of reactive oxygen species by complex II point to its overall importance in cellular physiology.

Aging-induced alterations in gene transcripts and functional activity of mitochondrial oxidative phosphorylation complexes in the heart

“…Complex II, succinate dehydrogenase (SDH), of the ETC is the membrane-bound component of the TCA cycle and is composed of 4 nuclear encoded subunits that are involved in the oxidation of succinate and electron transfer from FADH 2 to Coenzyme Q, thus linking the TCA cycle to the mitochondrial respiratory chain promoting electron flow, ATP production and reactive oxygen species generation (Cecchini, 2003). Despite downregulation of SDHC (p=0.002) and SDHD (p=0.007, Fig.…”

SNARE-fusion mediated insertion of membrane proteins into native and artificial membranes

“…In the next experiment, the artificial, water-soluble electron donor ubiquinone Q 1 was replaced with a native lipid-soluble analogue, ubiquinone Q 10 (E. coli uses Q 8 ). Under physiological conditions (in an aqueous solvent), long-chain ubiquinones such as Q 10 can only be enzymatically reduced, for example, in E. coli by complex I (NADH:Q oxidoreductase) or one of the two variants of complex II (succinate:formate dehydrogenase or fumarate reductase 15 ). The latter was purified and reconstituted in vesicles containing 1% (w/w) ubiquinol Q 10 and v-SNARE synaptobrevin.…”

Efficient Constrained Density Functional Theory Implementation for Simulation of Condensed Phase Electron Transfer Reactions

“…An orthogonalization procedure is then followed to arrive at a CDFT approximation of the coupling |H ab | which appears in the Marcus rate equation (1). 22,23 In order to estimate the required free energy quantities λ and ∆A, Warshel's 61 microscopic interpretation of Marcus theory is adopted.…”

“…Electron transfer (ET) reactions are ubiquitous in nature, serving a vital function in mitochondrial aerobic respiration [1][2][3] and a myriad of other redox processes in proteins. 4,5 Atomistic modeling of electron transfer kinetics is frequently founded on the linear response theory pioneered by Marcus,6 which has been extended to cover a wide range of phenomena 7,8 including ET processes at electrodes, 9,10 proton-coupled ET, 11 and reactions with large solvation changes.…”

“…A variety of theoretical methods are available for modeling the ET parameters in Equation (1). For |H ab |, these include the generalized Mulliken Hush (GMH) method, 14,15 localization and block diagonalization methods, [15][16][17][18][19][20][21] and constrained density functional theory (CDFT).…”