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beta-endorphin1-31 in the rat pituitary
O O Grigoriants1, D M Desiderio
1Charles B. Stout Neuroscience Mass Spectrometry Laboratory, The University of Tennessee, Memphis, USA.
International Journal of Peptide and Protein Research
|January 1, 1996
Summary
Rat pituitary beta-endorphin (BErat, 1-31) molecular mass differs from synthetic versions. Mass spectrometry suggests BErat, 1-31 has Ala at position 26, not Val.
Area of Science:
- Biochemistry
- Proteomics
- Endocrinology
Background:
- Beta-endorphin (BE) is a key peptide hormone involved in pain modulation and stress response.
- Accurate molecular characterization of endogenous peptides is crucial for understanding their function.
Purpose of the Study:
- To determine the precise molecular mass of rat pituitary beta-endorphin1-31 (BErat, 1-31).
- To compare the endogenous BErat, 1-31 with commercially available synthetic forms.
- To identify potential discrepancies in the amino acid sequence of BErat, 1-31.
Main Methods:
- Electrospray ionization mass spectrometry (ESIMS) for molecular mass determination.
- High-performance liquid chromatography (HPLC) for retention time analysis.
- Liquid secondary ion mass spectrometry (LSIMS) for tryptic fragment mass analysis.
Main Results:
- The measured molecular mass of endogenous BErat, 1-31 was 3435 ± 1 Da.
- This mass differed significantly from synthetic BErat, 1-31 (3465 ± 1 Da) but matched synthetic bovine beta-endorphin1-31 (BEbovine, 1-31).
- Analysis indicated the presence of Alanine (Ala) instead of Valine (Val) at position 26 in endogenous BErat, 1-31.
Conclusions:
- The amino acid sequence of endogenous BErat, 1-31 deviates from the DNA-predicted sequence.
- A post-translational modification or sequencing error likely accounts for the Ala substitution at position 26.
- This finding highlights the importance of direct molecular mass verification for peptide characterization.