Sequence determinants of cytosolic N-terminal protein processing.

Area of Science:

• Molecular Biology
• Proteomics
• Bioinformatics

Background:

• N-terminal methionine (Met) is the initiating amino acid for protein synthesis.
• Post-translational modification of N-terminal Met is crucial for protein function and stability.
• Sequence determinants governing N-terminal processing are not fully understood.

Purpose of the Study:

• To statistically analyze N-terminal methionine removal in prokaryotic and eukaryotic cytosolic proteins.
• To identify common sequence determinants controlling initiator Met processing.
• To investigate differences in N-terminal processing between prokaryotes and eukaryotes.

Main Methods:

• Statistical analysis of a large dataset of prokaryotic and eukaryotic cytosolic proteins.
• Sequence analysis focusing on residues adjacent to the initiator methionine.
• Correlation analysis between N-terminal residues and methionine removal/acetylation status.

Main Results:

• The amino acid residue adjacent to initiator Met is the primary determinant of its removal.
• Specific residues (Lys, Arg, Leu, Phe, Ile) protect Met from removal, while others (Ala, Gly, Pro, Ser, Thr, Val) promote its removal.
• Acetylation is biased towards Ala, Met, and Ser residues, with Asp being predominant before acetylated Met in eukaryotes.
• Significant differences exist in residue preferences between prokaryotic and eukaryotic N-terminal processing.
• Findings partially explain the mRNA consensus sequence around eukaryotic initiator AUG codons.

Conclusions:

• N-terminal methionine processing is sequence-dependent, with distinct rules in prokaryotes and eukaryotes.
• The adjacent amino acid residue plays a critical role in directing methionine removal and subsequent modifications.
• Understanding these determinants provides insights into protein maturation and translational regulation.