Combined plasma‐desorption mass spectrometry and Edman degradation applied to simultaneous sequence determination of isoforms of structural proteins from the cuticle of Locusta migratoria

Abstract

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.