An Investigation into Membrane Bound Redox Carriers Involved in Energy Transduction Mechanism in Brevibacterium linens DSM 20158 with Unsequenced Genome

P-type ATPases are membrane proteins acting as ion pumps that drive an active transport of cations across the membrane against a concentration gradient. The required energy for the ion transport is provided by binding and hydrolysis of ATP. A reaction mechanism of ion transport and energy transduction is assumed to be common for all P-type ATPases and generally described by the Post-Albers cycle. Transient currents and charge translocation of P-type ATPases were extensively investigated by electrical measurements that apply voltage jumps to initiate the reaction cycle. In this study, we simulate an applied voltage across the membrane by an electric field and perform electrostatic calculations in order to verify the experimentally-driven hypothesis that the energy transduction mechanism is regulated by specific structural elements. Side chain conformational and ionization changes induced by the electric field are evaluated for each transmembrane helix and the selectivity in response is qualitatively analyzed for the Ca2+-ATPase as well as for structural models of the Na+/K+-ATPase. Helix M5 responds with more conformer changes as compared to the other transmembrane helices what is even more emphasized when the stalk region is included. Thus our simulations support experimental results and indicate a crucial role for the highly conserved transmembrane helix M5 in the energy transduction mechanism of P-type ATPases.

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The antiporter-like subunit constituent of the universal adaptor of complex I, group 4 membrane-bound [NiFe]-hydrogenases and related complexes

Biological Chemistry ◽

10.1515/hsz-2012-0342 ◽

2013 ◽

Vol 394 (5) ◽

pp. 659-666 ◽

Cited By ~ 10

Author(s):

Ana P. Batista ◽

Bruno C. Marreiros ◽

Manuela M. Pereira

Keyword(s):

Structural Characteristic ◽

Complex I ◽

Energy Transduction ◽

Common Denominator ◽

Group 4 ◽

The Family ◽

Common Group ◽

Membrane Bound ◽

Α Helix

Abstract We have recently investigated the long-recognized relationship between complex I and group 4 [NiFe] hydrogenases and we have established the so-called Energy-converting hydrogenase related (Ehr) complex as a new member of the family. We have also observed that four subunits, homologues to NuoB, D, H and L, are common to the members of the family. We have designated this common group of subunits the universal adaptor. Taking into account the similarity of the Na+/H+ antiporter-like subunits of complex I (NuoL, NuoM and NuoN) and the unique structural characteristic of the long amphipathic α helix part of NuoL, the nature of the antiporter-like subunit of the universal adaptor was questioned. Thus, in this work we further explore the properties of the universal adaptor, investigating which antiporter-like subunit is part of the universal adaptor. We observe that the universal adaptor contains an antiporter-like subunit with a long amphipathic α helix, similar to NuoL. Consequently, the long helix is a common denominator that has been conserved in all members of the family. Such conservation surely reflects the key role of such helix in the energy transduction mechanism of this family of enzymes.

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Energy transduction by respiratory complex I – an evaluation of current knowledge

Biochemical Society Transactions ◽

10.1042/bst0330525 ◽

2005 ◽

Vol 33 (3) ◽

pp. 525-529 ◽

Cited By ~ 43

Author(s):

J. Hirst

Keyword(s):

High Resolution ◽

Complex I ◽

Structural Model ◽

Current Knowledge ◽

Energy Transduction ◽

Nadh:Ubiquinone Oxidoreductase ◽

Mechanistic Models ◽

Membrane Bound ◽

Respiratory Complex I ◽

Coherent Picture

Complex I (NADH:ubiquinone oxidoreductase) is a membrane-bound, multisubunit enzyme. At present, there is no high-resolution structural model available for complex I and its mechanism of energy transduction is unknown. However, the subunit compositions of complex I from both eukaryotic and prokaryotic organisms have been determined, the sequences of their subunits are known and a coherent picture of the redox cofactors present in complex I has been developed. Here, I aim to describe and examine data relating to the mechanism of complex I and to build a framework to facilitate the discussion of possible conclusions and mechanistic models.

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