Matrix assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometric (MS) analysis of purified Arachis hypogaea stem lectin (SL-I) and its tryptic digests suggested it to be an isoformic glucose/mannose binding lectin. Two-dimensional gel electrophoresis of SL-I indicated six isoforms (A1-A6), which were confirmed by Western blotting and MALDI-TOF MS analysis. Comparative analysis of peptide mass spectra of the isoforms matched with A. hypogaea lectins with three different accession numbers (Q43376_ARAHY, Q43377_ARAHY, Q70DJ5_ARAHY). Tandem mass spectrometric (MS/MS) analysis of tryptic peptides revealed these to be isoformic variants with altered amino acid sequences. Among the peptides, the peptide T12 showed major variation. The 199Val-Ser-Tyr-Asn202 sequence in peptide T12 of A1 and A2 was replaced by 199Leu-Ser-His-Glu202 in A3 and A4 (T12′) while in A5 and A6 this sequence was 199Val-Ser-Tyr-Val202 (T12″). Peptide T1 showed the presence of 10Asn in the isoforms A1-A5 while in A6 this amino acid was replaced by 10Lys (T1′). Overall amino acid sequence as identified by MS/MS showed a high degree of similarity between A1, A2 and among A3, A4, A5. Carbohydrate binding domain and adenine binding site seem to be conserved.
- MS/MS based peptide sequencing
- Mass spectrometry
- Peptide mass fingerprinting
ASJC Scopus subject areas