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Published on: July 14, 2015
Why are polar residues within the membrane core evolutionary conserved?
Kristoffer Illergård1, Anni Kauko, Arne Elofsson
1Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm bioinformatics Center, Stockholm University, SE-106 91 Stockholm, Sweden.
Polar residues in alpha-helical membrane proteins are rare but crucial for function. They are conserved due to their buried nature and direct involvement in protein activity, particularly in transporters and GPCRs.
Area of Science:
- Biochemistry and Structural Biology
- Membrane Protein Research
Background:
- Polar residues are generally less frequent within the hydrophobic membrane core of alpha-helical membrane proteins.
- These residues are often buried, with polar groups frequently bordering internal water-filled cavities.
Purpose of the Study:
- To investigate the distribution, functional roles, and conservation of polar residues in the membrane core.
- To develop a predictive method for identifying membrane-core polar residues from protein sequences.
Main Methods:
- Structural analysis of known alpha-helical membrane proteins.
- Functional role survey of identified polar residues.
- Sequence-based prediction method development.
Main Results:
- Polar residues in the membrane core are significantly conserved, more so than other core residues or external polar residues.
- Conservation is attributed to their buried location and direct functional involvement (e.g., binding, proton transfer, catalysis).
- Histidines interact with prosthetic groups; prolines facilitate conformational changes.
- Prediction method applied to human membrane proteins shows highest frequency in transporters and GPCRs.
Conclusions:
- Polar residues in membrane protein cores, though infrequent, play critical, conserved roles in protein function.
- The developed sequence-based method accurately predicts the prevalence of these residues in various membrane protein families.
- Findings highlight the importance of specific polar residues in membrane protein structure-function relationships and drug targeting.
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