Alexander Jussupow, Andrea Di Luca and Ville R. I. Kaila
Cardiolipin modulates the activity of membrane-bound respiratory enzymes that catalyze biological energy transduction. The respiratory complex I functions as the primary redox-driven proton pump in mitochondrial and bacterial respiratory chains, and its activity is strongly enhanced by cardiolipin. Read more
Alvin C. K. Teo, Sarah C. Lee, Naomi L. Pollock, Zoe Stroud, Stephen Hall, Alpesh Thakker, Andrew R. Pitt, Timothy R. Dafforn, Corinne M. Spickett & David I. Roper
Biological characterisation of membrane proteins lags behind that of soluble proteins. This reflects issues with the traditional use of detergents for extraction, as the surrounding lipids are generally lost, with adverse structural and functional consequences. Read more
2nd UK Workshop on Membrane Proteins: Solubilisation and Biophysical Characterisation
University of Leeds | 3 – 5 April 2019
CBMNet are sponsoring this Biochemical Society Training Event, a follow up to the successful workshop “Experimental Techniques for Studying Proteins and Lipids in Biological Membranes” held at Aston University in July – August 2018 (read the event report here). Read more
Yanli Qi Hui Liu Xiulai Chen Liming Liu
The microbial membrane serves as a biological barrier that separates the interior of cells from the external environment, thus playing an important role in tolerance to stress conditions during industrial bioprocessing. Read more
Itay Budin, Tristan de Rond, Yan Chen, Leanne Jade G. Chan, Christopher J. Petzold, Jay D. Keasling
Lipid composition determines the physical properties of biological membranes and can vary substantially between and within organisms. We describe a specific role for the viscosity of energy-transducing membranes in cellular respiration. Read more
Emmanuel Nji, Yurie Chatzikyriakidou, Michael Landreh & David Drew
Membrane bilayers are made up of a myriad of different lipids that regulate the functional activity, stability, and oligomerization of many membrane proteins. Despite their importance, screening the structural and functional impact of lipid–protein interactions to identify specific lipid requirements remains a major challenge. Read more
Royal Society Publishing has recently published a special issue of Interface Focus entitled “The artificial cell: biology-inspired compartmentalization of chemical function”, organised by Paul A Beales, Barbara Ciani and Stephen Mann.
This issue is based on a Royal Society Theo Murphy meeting held on the 26–27 February 2018. The articles reveal the rich diversity of research currently being undertaken in the field of artificial cell design and construction, and highlight the challenges that lie ahead.
The articles are FREE TO ACCESS here.
Membrane engineering via trans unsaturated fatty acids production improves Escherichia coli robustness and production of biorenewables
Constructing microbial biocatalysts that produce biorenewables at economically viable yields and titers is often hampered by product toxicity. For production of short chain fatty acids, membrane damage is considered the primary mechanism of toxicity, particularly in regards to membrane integrity. Previous engineering efforts in Escherichia coli to increase membrane integrity, with the goal of increasing fatty acid tolerance and production, have had mixed results. Herein, a novel approach was used to reconstruct the E. coli membrane by enabling production of a novel membrane component. Specifically, trans unsaturated fatty acids (TUFA) were produced and incorporated into the membrane of E. coli MG1655 by expression of cis-trans isomerase (Cti) from Pseudomonas aeruginosa. While the engineered strain was found to have no increase in membrane integrity, a significant decrease in membrane fluidity was observed, meaning that membrane polarization and rigidity were increased by TUFA incorporation. As a result, tolerance to exogenously added octanoic acid and production of octanoic acid were both increased relative to the wild-type strain. This membrane engineering strategy to improve octanoic acid tolerance was found to require fine-tuning of TUFA abundance. Besides improving tolerance and production of carboxylic acids, TUFA production also enabled increased tolerance in E. coli to other bio-products, e.g. alcohols, organic acids, aromatic compounds, a variety of adverse industrial conditions, e.g. low pH, high temperature, and also elevated styrene production, another versatile bio-chemical product. TUFA permitted enhanced growth due to alleviation of bio-product toxicity, demonstrating the general effectiveness of this membrane engineering strategy towards improving strain robustness.
Read the full article here.
One approach to experimental science involves creating hypotheses, then testing them by varying one or more independent variables and assessing the effects of this variation on the processes of interest. We use this strategy to compare the intellectual status and available evidence for two models or views of mechanisms of transmembrane drug transport into intact biological cells. One (BDII) asserts that lipoidal phospholipid Bilayer Diffusion Is Important, while a second (PBIN) proposes that in normal intact cells Phospholipid Bilayer diffusion Is Negligible (i.e. may be neglected quantitatively), because evolution selected against it, and with transmembrane drug transport being effected by genetically encoded proteinaceous carriers or pores, whose ‘natural’ biological roles and substrates are based in intermediary metabolism. Despite a recent review elsewhere, we can find no evidence able to support BDII as we can find no experiments in intact cells in which phospholipid bilayer diffusion was either varied independently or measured directly (although there are many papers where it was inferred by seeing a covariation of other dependent variables). By contrast, we find an abundance of evidence showing cases in which changes in the activities of named and genetically identified transporters led to measurable changes in the rate or extent of drug uptake. PBIN also has considerable predictive power, and accounts readily for the large differences in drug uptake between tissues, cells and species, in accounting for the metabolite-likeness of marketed drugs, in pharmacogenomics, and in providing a straightforward explanation for the late-stage appearance of toxicity and of lack of efficacy during drug discovery programmes despite macroscopically adequate pharmacokinetics. Consequently, the view that Phospholipid Bilayer diffusion Is Negligible (PBIN) provides a starting hypothesis for assessing cellular drug uptake that is much better supported by the available evidence.
Read more here.