Biological insertion of computationally designed short transmembrane segments

The great majority of helical membrane proteins are inserted co-translationally into the ER membrane through a continuous ribosome-translocon channel. The efficiency of membrane insertion depends on transmembrane (TM) helix amino acid composition, the helix length and the position of the amino acids within the helix. In this work, we conducted a computational analysis of the composition and location of amino acids in transmembrane helices found in membrane proteins of known structure to obtain an extensive set of designed polypeptide segments with naturally occurring amino acid distributions. Then, using an in vitro translation system in the presence of biological membranes, we experimentally validated our predictions by analyzing its membrane integration capacity. Coupled with known strategies to control membrane protein topology, these findings may pave the way to de novo membrane protein design.This work was supported by grants BFU2012-39482 to I.M. and BFU2010-19310/BMC and BFU2013-47736-P to M.A.M.-R. from the Spanish Ministry of Economy and Competitiveness (MINECO, co-financed by European Regional Development Fund), PROMETEOII/2014/061 from the Generalitat Valenciana to I.M., and by grants from the Swedish Foundation for Strategic Research, the European Research Council (ERC-2008-AdG 232648), the Swedish Cancer Foundation, the Swedish Research Council, and the Knut and Alice Wallenberg Foundation to GvH. C.B.-D. was recipient of a predoctoral FPI fellowship and an FPI short-staying grant from the MINECO to visit the laboratory of G.v.H