Primary structure of two major cuticular proteins from the migratory locust, Locusta migratoria, and their identification in polyacrylamide gels by mass spectrometry

The complete amino acid sequence has been determined for two proteins, LmAC P21 and LmACP22, which are prominent components of adult pharate cuticle fr om the migratory locust, Locusta migratoria. The proteins have relative mol ecular masses (M-r) of 16853 and 16879, respectively. They were purified by standard chromatographic methods, and the primary structures were determin ed by combined use of mass spectrometry and automatic Edman degradation. Th e proteins are characterized by the presence of a conserved, hydrophilic ce ntral sequence with pronounced similarity to sequences reported for cuticul ar proteins from other insect species, while the N- and C-terminal regions are dominated by the amino acids alanine, valine and proline. The electroph oretic identity of the two proteins was confirmed by matrix assisted laser desorption ionization mass spectrometry (MALDIMS) of the electroeluted LmAC P21/22 proteins from a two-dimensional electrophoresis gel. The mass spectr ometric analysis established the presence of additional proteins in close p roximity to the LmACP21/22 gel spot. One of these proteins, M-r 16134, was identified as LmACP18, and enzymatic digestion indicated that it is structu rally closely related to LmACP21 and LmACP22. (C) 1998 Elsevier Science B.V . All rights reserved.