Science at the Edge Seminar

Speaker: Marilyn Gunner, Physics Department, City College of New York

Title: Proton Pumping and Electron Tunneling to Power the Cell

Refreshments at 11:15 am.

Date: Fri, 17 Mar 2017, 11:30 am - 12:30 pm  

Type: Seminar

Location: 1400 BPS Bldg.

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Abstract:
A transmembrane proton gradient is established in cells by proton pumping through membrane embedded proteins from the N-side of the membrane, with fewer protons, to the more positive P-side. The energy to build the gradient comes from sunlight in photosynthesis or from energy liberated by redox chemistry such as in the reduction of oxygen in cytochrome c oxidase. The proton gradient fuels the transfer of ions and substrates across the membrane needed for cell signaling and metabolism and the production of ATP, the universal energy currency for biochemical reactions. To pump protons the protein must change the proton affinity of specific groups that serve as intermediate proton donors and acceptors. A hydrogen bond pathway connects proton donors and acceptors. The accessibility of proton transfer pathways to the N- and P-sides of the membrane must also change during the reaction cycle to ensure that the proton transfers do not dissipate the proton gradient. The gates that change the conductivity of proton transfer have been difficult to identify as they must be transient and may occur anywhere along the proton transfer pathways. MCCE (Multiconformation Continuum Electrostatics) has been used to access the proton affinity of key groups through the reaction cycle in cytochrome c oxidase and bacteriorhodopsin. Local structures in proteins that help groups gain and lose protons will be described.

References:

  • Molecular mechanisms for generating transmembrane proton gradients. (2013) MR Gunner, Muhamed Amin, Xuyu Zhu, Jianxun Lu. Biochim Biophys Acta 827:892-913. doi: 10.1016/ j.bbabio.2013.03.001
  • Characterizing the proton loading site in cytochrome c oxidase. (2014) Lu, J, Gunner, MR. Proc. Natl. Acad. Sci. USA 111(34):12414-9. doi: 10.1073/pnas.1407187111.
  • Halorhodopsin pumps Cl− and bacteriorhodopsin pumps protons by a common mechanism that uses conserved electrostatic interactions. Song Y, Gunner MR. Proc. Natl. Acad. Sci. USA 2014; DOI: 10.1073/pnas.1411119111.
  • The design features cells use to build their transmembrane proton gradient. Gunner, M.R. and Koder, R. (2016) Physical Biology. Phys. Biol. 2017 Feb 7;14(1):013001