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Solution structure of trypsin modulating oostatic factor is a left-handed helix
E V Curto1, M A Jarpe, J E Blalock
1Comprehensive Cancer Center, University of Alabama, Birmingham 35294.
Biochemical and Biophysical Research Communications
|June 15, 1993
Summary
The structure of trypsin modulating oostatic factor (TMOF), a mosquito hormone, was revealed as a rod-shaped helix. This finding challenges typical protein structure prediction rules.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Endocrinology
Background:
- Mosquitoes regulate digestive enzyme production, including trypsin-like enzymes, through hormonal signaling.
- Trypsin modulating oostatic factor (TMOF) is a decapeptide hormone crucial for terminating trypsin-like biosynthesis in mosquito midgut epithelial cells.
Purpose of the Study:
- To determine the solution structure of the TMOF decapeptide.
- To elucidate the structural basis for TMOF's function in regulating trypsin biosynthesis.
Main Methods:
- 2-D 1H nuclear magnetic resonance (NMR) spectroscopy was employed to analyze the peptide structure.
- Molecular modeling techniques were utilized to refine and interpret the NMR data.
Main Results:
- The TMOF peptide adopts a stable, rod-shaped left-handed helical conformation approximately 30 Å in length.
- Analysis revealed hydrophobic interactions between tyrosine 1 and proline 3, contributing to N-terminal stability.
- The observed structure deviates from the expected poly-L-proline beta-turn model and challenges standard chemical shift index (CSI) rules for secondary structure prediction.
Conclusions:
- The left-handed helical structure of TMOF provides an exception to typical CSI-based secondary structure assignments.
- The findings suggest that positive CSI indices, usually indicative of beta-strands, can also characterize left-handed poly-L-proline-like helices.
- This structural insight is vital for understanding TMOF's biological role and for developing novel insect control strategies.