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Related Experiment Videos

How hydrophobic is alanine?

IngMarie Nilsson1, Arthur E Johnson, Gunnar von Heijne

  • 1Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.

The Journal of Biological Chemistry
|May 23, 2003
PubMed
Summary

Alanine (Ala) shows a slight preference for the lipid-water interface in endoplasmic reticulum (ER) membranes. This finding, consistent across biochemical and biophysical methods, highlights early protein-lipid interactions in membrane protein assembly.

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Biophysics

Background:

  • Amino acids play a critical role in membrane protein integration.
  • Alanine is uniquely positioned regarding its influence on transmembrane alpha-helix insertion.
  • Understanding amino acid behavior at membrane interfaces is key to protein folding and assembly.

Purpose of the Study:

  • To investigate the partitioning preference of alanine at the endoplasmic reticulum (ER) membrane interface.
  • To compare alanine's role in promoting helical hairpin formation versus its position within transmembrane helices.
  • To correlate biochemical findings with existing biophysical data on amino acid partitioning.

Main Methods:

  • Assessing alanine's ability to promote helical hairpin formation in ER membranes.
  • Mapping the position of alanine residues within transmembrane alpha-helices relative to the membrane.
  • Comparing experimental results with published pentapeptide partitioning data in model systems.

Main Results:

  • Biochemical assays indicated a weak but distinct preference for alanine to partition into the lipid-water interface region.
  • Mapping studies confirmed alanine's tendency to favor the membrane interface over the acyl chain core.
  • Results align with biophysical measurements of pentapeptide partitioning in simpler lipid environments.

Conclusions:

  • Biochemical and biophysical data converge, showing alanine's preference for the membrane interface.
  • Protein-lipid interactions are significant even in the initial stages of membrane protein assembly in the ER.
  • The translocon-mediated insertion process is influenced by these early protein-lipid interactions.

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