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A novel, highly hydrophobic, glycine-and proline-rich peptide was characterized in the ovary of the desert locust, Schistocerca gregaria. The peptide was detected as one of the major peaks in a chromatographic separation of an acidic methanolic extract of 50 mature ovaries. Electrospray mass spectrometry yielded a molecular mass of 6305 Da. The partial amino acid sequence as determined by Edman degradation based automated microsequencing is as follows: Ala-Tyr-Pro-Ala-Ala-His-Gln-Gly-Tyr-Pro-Ala-His-Val-Gly-Tyr-Ala-Arg-Val-Gly-Gly-Tyr-Pro-Ser-Tyr-Gly-Tyr-Pro-Ala. Four amino acids (Gly, Pro, Ala, and Tyr) account for more than 80% of the composition of this sequence. Gly-Tyr-Pro is the most important repetitive motif. Ala-Tyr-Pro, Gly-Tyr-Gly and Gly-Tyr-Ala occur as variations of this motif. The novel glycine-and proline-rich insect peptide displays structural characteristics similar to those of a new class of glycine-and proline-rich proteins (GPRP) that have recently been identified in Arabidopsis thaliana (thale cress) and Daucus carota (carrot). The GPRP of A. thaliana contains the same repetitive motifs (except for Ala-Tyr-Pro), the Gly-Tyr-Pro motif also being the most abundant. (C) 1998 Academic Press.