Insect neuropeptides

Biju, V, Muraleedharan, D., Nakayama, K, Shinohara, Y., Itoh, T., Baba, Y. and Ishikawa, M. (2007) Quantum dot-insect neuropeptide conjugates for fluorescence imaging, transfection, and nucleus targeting of living cells. Langmuir, 23, 10254-10261. 

Using the C-terminal hexapeptide of substance P as a model compound, each one of cycloscan diversity parameters have been shown to affect the conformation and hence the biological activity of the peptide.1417,470,4711 This approach has been successfully applied to various peptides such as somatostatin,14191 the insect neuropeptide pheromone biosynthesis activating neuropeptide (PBAN),1420,4311 BPTI,14351 and on the nuclear localization signal (NLS) of the HIV-1 matrix protein (MA),14291 and HIV-1 Tat/Rev.14301... 

Elliott J. T., Jurenka R. A., Prestwich G. D. and Roelofs W. L. (1997) Identification of soluble binding proteins for an insect neuropeptide. Biochem. Biophys. Res. Commun. 238, 925-930. 

Nachman R. J., Holman G. M. and Cook B. J. (1986) Active fragments and analogs of the insect neuropeptide leucopyrokinin structure-function studies. Biochem. Biophys. Res. Commun. 137, 936-942. 

Raina A. K., Kempe, T. G. and Jaffe H. (1991) Pheromone biosynthesis-activating neuropeptide Regulation of pheromone production in moths. In Insect Neuropeptides Chemistry, Biology and Action, eds J. J. Menn, T. J. Kelly and E. P. Masler, pp. 100-109. American Chemical Society, Washington, DC. 

Schoofs L., Holman G. M., Hayes T. K., Tips A., Vandesande F. and Loof A. D. (1990b) Isolation, identification and synthesis of locustamyotropin (Lom-MT), a novel biologically active insect neuropeptide. Peptides 11, A21—A33. 

Zdarek J., Nachman R. J. and Hayes T. K. (1997) Insect neuropeptides of the pyrokinin/ PB AN family accelerate pupariation in the fleshfly (Sarcophaga bullata) larvae. Anna. NY Acad. Sci. 814, 67-72. 

As the senior editor (Julius J. Menn), I extend my deepest appreciation to Herbert Roller, whose foresight, knowledge, and inspiration were instrumental in introducing me to the exciting field of insect neuropeptides. 

The cover illustration is based on a model of two related insect neuropeptide active core regions in a fi-tum conformation generated from molecular dynamics on a Cray stq>ercomputer. 

In recent years, the improvement of appropriate techniques has facilitated the chemical identification of a number of insect neuropeptides as well as comparison with their respective counterparts in vertebrates. Among these are metabolic, myotropic, allatotropic, and allatostatic factors. 

A small number of ancestral proteins encoded by ancestral genes may have given rise to a multiplicity of active peptides in concert with the evolution of complementary receptor molecules. Our current knowledge of insect neuropeptides is consistent with and actually supports these views. 

Because of the rapidly developing nature of the field, periodic symposia, such as the one on which this volume is based, will likely proliferate in the next few years in an effort to keep researchers focused on current developments. Such symposia will become more specialized, attending to areas such as sequenced peptides, insect neuropeptide molecular genetics, peptide families, insect neuropeptide processing, and so forth. In this overview, some recent developments in bioactive peptide research are considered, as are directions where such developments may lead. 

The elucidation of the primary structures of proctolin (22) and AKH (2Q), signaled the beginning of the structural identification of insect neuropeptides. These relatively small peptides (pentapeptide proctolin and decapeptide AKH) remained the only known insect peptide sequences for a number of years until, in the early 1980 s, accumulated technical advances in peptide isolation and microsequencing techniques facilitated the analysis of insect peptides (8-12 ... 

Table 1. Bioacdve Insect Neuropeptides for which Partial or Entire Gene Stnictuies are Reported...

To be sure, molecular genetics suffers from limitations. Many of its methods cannot be used without the availability of at least one known amino acid sequence. Thus, peptide isolation remains a critical need. Oligonucleotide probes can be too short, leading to useless or "false positive" hybridizations. Also, an appropriate bioassay is required to assess the authenticity of any product of molecular biology. However, the use of molecular genetic techniques will cause an explosion of information on insect neuropeptides and their sequences within the very near future. 

The processes of prepropolypeptide synthesis, translocation, proteolytic processing and non-proteolytic modification can be enzymatically defined. These definitions are continuing to be developed and clarified. There are limited reports on insect neuropeptide processing (101.102. but these investigations should increase rapidly with the identification of precursor sequences via molecular genetics. The identification of processing enzymes, both proteolytic and non-proteolytic, will further open whole new areas for exploration. 

In the early 1980 s, dramatic Improvements in both peptide isolation technology and the instrumentation for structural characterization resulted in an avalanche of new insect neuropeptide structures. Of the 50-60 known structures, about half exhibit effects on the contractile activity of insect visceral muscle at physiological concentrations. This report describes the strategies and tactics that were utilized to successfully isolate, purify, and structurally characterize this group of insect neuropeptides. 

The remainder of this report describes how these visceral muscle bioassays were used to successfully isolate and structurally characterize more than two dozen insect neuropeptides. 

Structurally, corazonin does not seem to fit into any of the known insect neuropeptide families. The presence of a polar arginine residue and the absence of a Phe residue at position 4 exclude corazonin from the AKH family, while the absence of the C-terminal pentamer, Phe-X-Pro-Arg-Leu-NH2, excludes corazonin from the leucopyrokinin peptide family discussed later in this report. 

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