C-terminal Elongation of Growth-blocking Peptide Enhances Its Biological Activity and Micelle Binding Affinity

Yoshitaka Umetsu,Tomoyasu Aizawa,Kaori Muto,Hiroko Yamamoto,Masakatsu Kamiya,Yasuhiro Kumaki,Mineyuki Mizuguchi,Makoto Demura,Yoichi Hayakawa,Keiichi Kawano

doi:10.1074/jbc.m109.011148

Abstract

Growth-blocking peptide (GBP) is a hormone-like peptide that suppresses the growth of the host armyworm. Although the 23-amino acid GBP (1-23 GBP) is expressed in nonparasitized armyworm plasma, the parasitization by wasp produces the 28-amino acid GBP (1-28 GBP) through an elongation of the C-terminal amino acid sequence. In this study, we characterized the GBP variants, which consist of various lengths of the C-terminal region, by comparing their biological activities and three-dimensional structures. The results of an injection study indicate that 1-28 GBP most strongly suppresses larval growth. NMR analysis shows that these peptides have basically the same tertiary structures and that the extension of the C-terminal region is disordered. However, the C-terminal region of 1-28 GBP undergoes a conformational transition from a random coiled state to an alpha-helical state in the presence of dodecylphosphocholine micelles. This suggests that binding of the C-terminal region would affect larval growth activity.

Highlights

Parasitization by wasp induces an elevation of Growth-blocking peptide (GBP) in the last larval stages
A cDNA analysis indicated that the cDNA encodes a 23-amino acid GBP (1–23 GBP), GBP purified from parasitized armyworm plasma consists of 25 amino acid residues
Our results suggest that the elongation of the C-terminal region of Phe23–Thr28 greatly reinforced GBP binding with the membrane

Summary

1–23 GBP 1–25 GBP 1–28 GBP

ENFSG GCVAG YMRTP DGRCK PTF ENFSG GCVAG YMRTP DGRCK PTFYQ ENFSG GCVAG YMRTP DGRCK PTFYQ LIT structure predictions. In this study we focused on the C terminus region of GBP and analyzed its contribution to the expression of some biological activities and to the tertiary structure of this peptide. We prepared GBP with 28 amino acids and characterized the C-terminal region of 1–28 GBP (residues Phe23–Thr28), because we knew that GBP is present as a 23-amino acid peptide in nonparasitized healthy larvae and that GBP with 28 amino acids has been found only in parasitized host larvae. Our results suggest that the elongation of the C-terminal region of Phe23–Thr greatly reinforced GBP binding with the membrane. The elongation increased GBP inhibition of larval growth

EXPERIMENTAL PROCEDURES

RESULTS AND DISCUSSION

1–23 GBP 1–28 GBP structure of 1–25 GBP in aqueous solution was previously