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A database analysis of potential glycosylating Asn-X-Ser/Thr consensus sequences
T H Christlet1, M Biswas, K Veluraja
1Department of Physics, Manonmaniam Sundaranar University, Tirunelveli 627 012, Tamil Nadu, India. bio@md3.vsnl.net.in
Summary
Glycine, asparagine, and phenylalanine are preferred at the X position in glycosylation sequences. This preference, along with specific conformational angles, suggests their functional significance in protein glycosylation.
Area of Science:
- Biochemistry
- Structural Biology
- Proteomics
Background:
- The Asn-X-Ser/Thr motif is a consensus sequence for N-linked glycosylation in proteins.
- Understanding the factors influencing the selection of residues at the X position is crucial for predicting and understanding glycosylation.
- The three-dimensional structure of proteins provides insights into the accessibility and conformational preferences of this motif.
Purpose of the Study:
- To analyze the frequency and preferences of amino acid residues at the X position of the Asn-X-Ser/Thr glycosylation consensus sequence.
- To investigate the structural and conformational factors influencing the selection of residues at the X position.
- To determine the role of specific amino acids and their local conformation in the N-glycosylation process.
Main Methods:
- Analysis of the Protein Data Bank (PDB) database for non-homologous proteins containing the Asn-X-Ser/Thr motif.
- Calculation of a deviation parameter (DP) to quantify residue selection preference at the X position.
- Analysis of Ramachandran (Phi,Psi) angles and dihedral angles for residues within the consensus sequence.
- Identification of hydrogen bonding interactions between residues and the peptide backbone.
Main Results:
- Over 65% of Asn residues in the consensus sequence are located on the protein surface, indicating potential for glycosylation.
- Glycine, asparagine, and phenylalanine exhibit statistically significant positive deviation parameters (DP) at the X position.
- Glycine's presence is associated with specific, disallowed Ramachandran angles for other residues, suggesting a conformational role.
- Analysis of confirmed N-glycosylation sites revealed nine distinct conformational states, often involving direct or water-mediated hydrogen bonds between Asn and Ser/Thr.
Conclusions:
- Specific amino acids, particularly Glycine, Asparagine, and Phenylalanine, are preferentially selected at the X position of the glycosylation motif.
- The conformational flexibility and hydrogen bonding potential around the consensus sequence play a critical role in N-glycosylation.
- The findings provide insights into the structural basis of N-glycosylation site selection and may aid in predicting glycosylation patterns.