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Membrane proteins are dramatically less conserved than water-soluble proteins across the tree of life

Pomiankowski, A; Lane, N; Sojo, V; Dessimoz, C; (2016) Membrane proteins are dramatically less conserved than water-soluble proteins across the tree of life. Molecular Biology and Evolution , 33 (11) pp. 2874-2884. 10.1093/molbev/msw164. Green open access

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Abstract

Membrane proteins are crucial in transport, signaling, bioenergetics, catalysis, and as drug targets. Here we show that membrane proteins have dramatically fewer detectable orthologs than water-soluble proteins, less than half in most species analyzed. This sparse distribution could reflect rapid divergence or gene loss. We find that both mechanisms operate. First, membrane proteins evolve faster than water-soluble proteins, particularly in their exterior- facing portions. Second, we demonstrate that predicted ancestral membrane proteins are preferentially lost compared with water-soluble proteins in closely related species of archaea and bacteria. These patterns are consistent across the whole tree of life, and in each of the three domains of archaea, bacteria, and eukaryotes. Our findings point to a fundamental evolutionary principle: membrane proteins evolve faster due to stronger adaptive selection in changing environments, while cytosolic proteins are under more stringent purifying selection in the homeostatic interior of the cell. This effect should be strongest in prokaryotes, weaker in unicellular eukaryotes (with intracellular membranes), and weakest in multicellular eukaryotes (with extracellular homeostasis). We demonstrate that this is indeed the case. Similarly, we show that extracellular water-soluble proteins exhibit an even stronger pattern of low homology than membrane proteins. These striking membrane proteins versus water-soluble proteins have important implications for evolution and medicine.

Type: Article
Title: Membrane proteins are dramatically less conserved than water-soluble proteins across the tree of life
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/molbev/msw164
Publisher version: http://dx.doi.org/10.1093/molbev/msw164
Language: English
Additional information: © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Keywords: membrane proteins, orthologs, homeostasis, evolution, adaptation
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Genetics, Evolution and Environment
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1503896
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