Protein sequences yield a proteomic code.

Area of Science:

• Structural biology
• Genomics
• Proteomics

Background:

• Crystallized protein structures reveal organization into consecutively connected units of 25-35 residues.
• These units are characterized as closed loops, where the polypeptide chain returns to a close contact with itself.

Purpose of the Study:

• To propose a novel view of globular proteins as loop fold structures.
• To investigate the evolutionary connections and sequence characteristics of these protein units.

Main Methods:

• Analysis of crystallized protein structures.
• Positional autocorrelation analysis of protein sequences from prokaryotic genomes.
• Identification and structural analysis of prototype sequence matches in crystallized proteins.

Main Results:

• A universal feature of globular proteins is their organization into 25-35 residue closed loop units.
• The same unit size is detected in prokaryotic genomes, indicating evolutionary links.
• Prototype sequences for these units were identified, with matches found in crystallized proteins, often forming closed loops.

Conclusions:

• Globular proteins can be fundamentally viewed as loop fold structures.
• The identified units suggest an evolutionary connection and a limited spectrum of sequence prototypes, potentially forming a proteomic code.