Raymond Valentine

Omega-3 Fatty Acids and the DHA Principle

Introduction Molecular Biology of Omega-3 Chains as Structural Lipids: Many Central Questions Remain Unanswered Evolution of DHA and the Membrane Darwinian Selection of the Fittest Membrane Lipids: From Archaeal Isoprenoids to DHA-Enriched Rhodopsin Disks Coevolution of DHA Membranes and Their Proteins Convergent Evolution of DHA/EPA Biosynthetic Pathways Membrane Evolution in a Marine Bacterium: Capitalizing on DHA for Energy Conservation in Seawater Evolution of DHA Membranes in Human Neurons General Properties of Omega-3s and Other Membrane Lipids DHA/EPA Chains as Powerful Membrane Antifreeze DHA as a Mediocre Permeability Barrier against Cations: Water Wire Theory DHA/EPA Membranes as Targets of Oxidative Damage Cellular Biology of Omega-3s and Other Membrane Lipids Bacteria: Environmental Modulation of Membrane Lipids for Bioenergetic Gain Chloroplasts: Harnessing DHA/EPA for Harvesting Light in the Sea Mitochondria: DHA-Cardiolipin Boosts Energy Output Sperm: Essential Roles of DHA Lead to Development of a Mechanical Stress Hypothesis Lessons and Applications DHA/EPA Mutualism between Bacteria and Marine Animals Membrane Adaptations for an Oily Environment: Lessons from a Petroleum-Degrading Bacterium Lessons from Yeast: Phospholipid Conformations Are Important in Winemaking DHA Principle Applied to Global Warming DHA Principle Applied to Molecular Farming DHA/Unsaturation Theory of Aging DHA Principle Applied to Neurodegenerative Diseases Dietary DHA in Prevention of Colon Cancer: How a Risk to the Cell Benefits the Organism Index

Important roles for membrane lipids in haloarchaeal bioenergetics.

Recent advances in lipidomic analysis in combination with various physiological experiments set the stage for deciphering the structure-function of haloarchaeal membrane lipids. Here we focused primarily on changes in lipid composition of Haloferax volcanii, but also performed a comparative analysis with four other haloarchaeal species (Halobacterium salinarum, Halorubrum lacusprofundi, Halorubrum sodomense and Haloplanus natans) all representing distinctive cell morphologies and behaviors (i.e., rod shape vs. pleomorphic behavior). Common to all five haloarchaea, our data reveal an extraordinary high level of menaquinone, reaching up to 72% of the total lipids. This ubiquity suggests that menaquinones may function beyond their ordinary role as electron and proton transporter, acting simultaneously as ion permeability barriers and as powerful shield against oxidative stress. In addition, we aimed at understanding the role of cations interacting with the characteristic negatively charged surface of haloarchaeal membranes. We propose for instance that by bridging the negative charges of adjacent anionic phospholipids, Mg2+ acts as surrogate for cardiolipin, a molecule that is known to control curvature stress of membranes. This study further provides a bioenergetic perspective as to how haloarchaea evolved following oxygenation of Earths atmosphere. The success of the aerobic lifestyle of haloarchaea includes multiple membrane-based strategies that successfully balance the need for a robust bilayer structure with the need for high rates of electron transport - collectively representing the molecular basis to inhabit hypersaline water bodies around the planet.

Phospholipids and glycolipids mediate proton containment and circulation along the surface of energy-transducing membranes.

Proton bioenergetics provides the energy for growth and survival of most organisms in the biosphere ranging from unicellular marine phytoplankton to humans. Chloroplasts harvest light and generate a proton electrochemical gradient (proton motive force) that drives the production of ATP needed for carbon dioxide fixation and plant growth. Mitochondria, bacteria and archaea generate proton motive force to energize growth and other physiologies. Energy transducing membranes are at the heart of proton bioenergetics and are responsible for catalyzing the conversion of energy held in high-energy electrons→electron transport chain→proton motive force→ATP. Whereas the electron transport chain is understood in great detail there are major gaps in understanding mechanisms of proton transfer or circulation during proton bioenergetics. This paper is built on the proposition that phospho- and glyco-glycerolipids form proton transport circuitry at the membranes surface. By this proposition, an emergent membrane property, termed the hyducton, confines active/unbound protons or hydronium ions to a region of low volume close to the membrane surface. In turn, a von Grotthuß mechanism rapidly moves proton substrate in accordance with nano-electrochemical poles on the membrane surface created by powerful proton pumps such as ATP synthase.