COMBINED PLASMA-DESORPTION MASS-SPECTROMETRY AND EDMAN DEGRADATION APPLIED TO SIMULTANEOUS SEQUENCE DETERMINATION OF ISOFORMS OF STRUCTURAL PROTEINS FROM THE CUTICLE OF LOCUSTA-MIGRATORIA

The primary structures of two basic low-molecular-mass proteins, Lm-67 and Lm-70 from the pharate cuticle of the migratory locust, Locusta migratoria, were determined. The sequencing strategy was based on combined use of plasma-desorption mass spectrometry (PDMS) and automatic Edman degradation of the proteins and their enzymically derived peptides. The mass-spectral data showed the presence of two proteins in each preparation. For protein preparation Lm-67, this was indicated by the mass spectrum of the intact protein. For protein preparation Lm-70, the presence of two variants only became evident by mass-spectrometric analysis of the enzymically derived peptides. Both proteins show strong similarity to other exocuticular proteins from L. migratoria.