A New Member of the Growth-Promoting Glycoproteins from Diaprepes Root Weevil (Coleoptera: Curculionidae)

Zhipeng Huang, Wayne B. Hunter, Cathy A. Cleland, Murray Wolinsky, Stephen L. Lapointe, Charles A. Powell

Abstract


A new member belonging to the family of growth-promoting glycoproteins referred to as imaginal disc growth factors, IDGF, was identified from the root weevil Diaprepes abbreviatus (L.), (Coleoptera: Curculionidae). The imaginal disc growth factor full length cDNA transcript, designated as idgf-DRW, was cloned and identified from tissue of adult, teneral DRW females. Sequencing and subsequent homology comparisons of the nucleotide sequence (GenBank accession no. AY821658) indicated that the open reading frame (ORF) consisted of 1329 bases and encoded a putative protein of 442 amino acid residues with a calculated molecular weight of 49.5 kDa and a pI value of 6.68. BLASTX comparisons of the idgf-DRW cDNA sequence showed that the deduced amino acid sequence designated as IDGF-DRW (AAV68692.1) had 43% to 51% similarity with IDGF1-5 and DS47 from Drosophila melanogaster, D. simulans, and D. yakuba, 51% similarity with IDGF in Pieris rapae, and 51% similarity with an IDGF-like protein in Bombyx mori. Signal P analysis revealed that the predicted IDGF-DRW contained a signal peptide of 23 amino acid residues located at the N-terminus, similar to other known IDGF proteins. The structure of IDGF-DRW was predicted based on the characterized IDGF2 from D. melanogaster as the model. The deduced amino acid sequence for the IDGF-DRW protein had 48% similarity with Drosophila melanogaster IDGF2. The predicted IDGF-DRW displays the characteristics found in Drosophila IDGFs, the fold of family 18 glycosyl hydrolases, with an insertion (Gly304 to Phe392) in the beta barrel between strand ß7 and helix alpha-7 that forms an additional a+ß domain similar to that of Serratia marcescens chitinases A and B. An identified nucleotide change which results in an amino acid change within the active binding site in IDGF-DRW also was observed. The significant similarities of IDGF-DRW to other members within the family of IDGFs support its classification as a new member of the invertebrate growth factors and the first IDGF to be identified from a coleopteran.

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