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Updated: Aug 20, 2026

Reconstitution of Msp1 Extraction Activity with Fully Purified Components
Published on: August 10, 2021
Membrane transport proteins with complete replacement of transmembrane helices with polyalanine sequences remain
Xiaoyong Bao1, Yongyue Chen, Sung Haeng Lee
1Department of Neuroscience and Cell Biology and the Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, Texas 77555-0437, USA.
Abstract:
Approximately 25% of all genome coding sequences correspond to membrane proteins, which perform varied and essential functions in cells. Eukaryotic integral membrane proteins are predominantly alpha-helical proteins that span the membrane several times. The most frequent approach to identifying transmembrane-helix amino acids essential for function is to substitute native residues, one at a time, with Cys or Ala (Cys- and Ala-scanning mutagenesis). Here, we present a new approach, in which complete transmembrane-helix native sequences are substituted with poly-Ala sequences. We show that the basic functional features of two dissimilar membrane proteins, which function as a channel and a pump, respectively, are maintained when certain individual alpha-helices are replaced with poly-Ala sequences. This approach ("helix-scanning mutagenesis") allows for rapid identification of helices containing residues essential for function and can be used as a primary helix-screening tool, followed by individual amino acid substitutions when specific helix poly-Ala replacements cause functional changes in the protein.
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