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Removal of N-terminal blocking groups from proteins
Joseph W Leone1, Brian Hampton2, Elizabeth Fowler3
1Pfizer VMRD, Kalamazoo, Michigan.
Current Protocols in Protein Science
|March 15, 2011
Summary
This study presents two enzymatic methods for N-terminal protein sequence analysis. These methods, using pyroglutamate aminopeptidase and acylaminoacyl-peptide hydrolase, effectively unblock proteins for sequencing.
Area of Science:
- Biochemistry
- Proteomics
- Analytical Chemistry
Background:
- N-terminal protein sequencing is crucial for protein identification and characterization.
- Protein N-termini are often blocked by acyl modifications, hindering direct sequencing.
- Existing methods for unblocking proteins can be inefficient or incompatible with certain modifications.
Purpose of the Study:
- To present robust enzymatic methods for the N-terminal sequence analysis of blocked proteins.
- To provide detailed protocols for unblocking proteins with pyroglutamate or other acyl groups.
- To enable efficient protein sequencing through effective removal of N-terminal blocking groups.
Main Methods:
- Enzymatic cleavage using pyroglutamate aminopeptidase for N(α)-pyrrolidone carboxyl-proteins.
- Enzymatic cleavage using acylaminoacyl-peptide hydrolase for N(α)-acyl-proteins.
- Chemical blocking of newly generated peptides with succinic anhydride or phenylisothiocyanate/performic acid prior to hydrolase treatment.
- Colorimetric assay for pyroglutamate aminopeptidase activity.
Main Results:
- Demonstrated successful application of pyroglutamate aminopeptidase for N-terminal unblocking in solution and on membranes.
- Established a protocol for acylaminoacyl-peptide hydrolase application on fragmented and re-blocked peptides.
- Showcased the selective substrate specificity of acylaminoacyl-peptide hydrolase for the N-terminal peptide.
Conclusions:
- The presented enzymatic methods offer reliable strategies for N-terminal sequence analysis of diverse blocked proteins.
- These protocols enhance the scope of protein sequencing by addressing common N-terminal modifications.
- The described techniques are valuable tools for proteomics research and protein characterization.
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