NORSp

NORSp predicts NOn-Regular Secondary Structure (NORS) regions by identifying disordered protein segments lacking regular secondary structure, specifically stretches without defined alpha-helices or beta-sheets, from amino acid sequences.

Key Features:

• NORS Detection Threshold: Identifies stretches of more than 70 consecutive residues without defined alpha-helices or beta-sheets.
• Long-region Recognition: Detects NORS regions that often exceed 150 residues in length.
• Secondary-structure and Motif Evaluation: Evaluates predicted secondary structures, transmembrane helices, and coiled-coil formations within input sequences.
• Amino Acid Composition Analysis: Distinguishes the amino acid composition of NORS regions from structured loops characterized in the Protein Data Bank (PDB).
• Taxonomic Prevalence: Captures the observation that NORS regions are frequent in eukaryotic proteins and less prevalent in prokaryotes and archaea.
• Evolutionary Conservation: Notes that NORS regions can exhibit evolutionary conservation comparable to their surrounding sequences.
• Functional Association: Associates NORS regions with regulatory and transcription-related activities and lower association with biosynthesis and energy metabolism.
• Interaction Propensity: Reflects that proteins containing NORS regions tend to have a higher number of interaction partners.

Scientific Applications:

• Conformational Studies: Identifying proteins that may adopt unique structural conformations upon binding or interaction.
• Protein–Protein Interaction Analysis: Prioritizing regions likely to mediate multiple interaction partners in interaction-network studies.
• Functional Annotation: Annotating proteins involved in regulatory and transcription-related activities versus those involved in biosynthesis and energy metabolism.
• Comparative Proteomics: Comparing prevalence and properties of disordered NORS regions across eukaryotic, prokaryotic, and archaeal proteomes.

Methodology:

Analyzes protein sequences to identify stretches of >70 consecutive residues lacking defined alpha-helices and beta-sheets and evaluates predicted secondary structure, transmembrane helices, and coiled-coil formations.